Surprisingly common in fangames and mods. Mushroom Kingdom Fusion started in 2007 at the latest, and it's not going to be done for a year or so at the earliest. So, 20 years, maybe 30 if you count predecessor projects.
Brutal Mario started in 2006 at the latest, and ended in the 2020s as far as I recall, so about 14-15 years. Of course, the 2006 demo was technically demo 6, so we have no idea when the first 5 versions were created since they seem to be gone forever.
Super Mario Star World is a remake/sequel to the Mario 64 hack Super Mario Star Road, which was made for Super Mario 64 DS instead. It seemed to start out as a sequel in the Super Mario 64 engine in 2013, then ended up as a Super Mario 3D Land mod a few years later, got retooled as a Super Mario 64 DS hack a few years after that and is currently in development by a new creator after original creator SKELUX got cancer and moved onto other projects.
In other mediums, I guess there's the Thief & the Cobbler. Started in 1964, got an unfinished/messed up release in 1993, and a better recuts in 2013 and 2023.
Video games in general have lots of people working on their games for decades too. UnReal World is from early 90s, was released on Steam in 2016, and AFAIK still gets updates. Nethack is even older (late 80s?) and also still get updates, I guess there might be bunch of MUD with single creators who still churn out updates too. Dwarf Fortress is quite old too for still gaining in popularity.
Oh video games in general can have crazy development times, whether it's through an open beta/development process or a closed one. Dwarf Fortress is a good one for sure, as is Star Citizen. Also Duke Nukem Forever, and Beyond Good & Evil 2 (the latter has somehow passed the former's record for longest recognised game development time at 20 years compared to 14).
Super Mario Bros X is arguably getting up there too, started in 2009 by Terraria developer Redigit, and now in development by a new group as of 2026.
And while a Doom fan needs to check this, I remember the mod Mordeth started before Duke Nukem Forever was announced, and the later episodes ain't done as of 2026.
I'm reminded of an old talk by Rich Hickey [1] (he created Closure, initially in semi-isolation over some years).
> When was the last time that you thought about something for an
> entire hour? ... Howabout for a whole day? ... or over the course of a
> month? ... or a year? These are tremendously valuable moments, if you
> get to have them at all.
I think Charles Babbage is a special case -- IIRC his son also picked up his work, after his death. So he actually worked on it for "generations", by having a child who also worked on his ideas :-)
Darwin took 21 years to publish his findings on evolution. In fact he couldn't finish the actual book that he had set out to write and published a summarized abstract instead, which is what we know as On the Origin of Species.
Plus he would have kept working on it until Alfred Wallace wrote him a letter about coming up with his own idea independently so it was publish together or get beat to the punch.
A couple software examples off the top of my head are Richard Hipp with SQLite and Matthew Ahrens with ZFS. Both almost incomprehensibly sophisticated projects executed well over decades.
Neither are anything like a solo effort in the way these examples are, and it's hard to say what they'd be like without the long individual involvement.
"Few paintings have lasted the test of time as the great wave of Kanagawa. It took Kanagawa 40 years before he drew the wave he is most known for."
The painting is by Hokusai. Kanagawa is a place.
He doesn't do much better on the other example. Term-frequency saturation is the important part, and he ignores the 1972 paper by Karen Sparck Jones.
He also made the Kessel Run in less than twelve parsecs.
Surprisingly common in fangames and mods. Mushroom Kingdom Fusion started in 2007 at the latest, and it's not going to be done for a year or so at the earliest. So, 20 years, maybe 30 if you count predecessor projects.
Brutal Mario started in 2006 at the latest, and ended in the 2020s as far as I recall, so about 14-15 years. Of course, the 2006 demo was technically demo 6, so we have no idea when the first 5 versions were created since they seem to be gone forever.
Super Mario Star World is a remake/sequel to the Mario 64 hack Super Mario Star Road, which was made for Super Mario 64 DS instead. It seemed to start out as a sequel in the Super Mario 64 engine in 2013, then ended up as a Super Mario 3D Land mod a few years later, got retooled as a Super Mario 64 DS hack a few years after that and is currently in development by a new creator after original creator SKELUX got cancer and moved onto other projects.
In other mediums, I guess there's the Thief & the Cobbler. Started in 1964, got an unfinished/messed up release in 1993, and a better recuts in 2013 and 2023.
Video games in general have lots of people working on their games for decades too. UnReal World is from early 90s, was released on Steam in 2016, and AFAIK still gets updates. Nethack is even older (late 80s?) and also still get updates, I guess there might be bunch of MUD with single creators who still churn out updates too. Dwarf Fortress is quite old too for still gaining in popularity.
Oh video games in general can have crazy development times, whether it's through an open beta/development process or a closed one. Dwarf Fortress is a good one for sure, as is Star Citizen. Also Duke Nukem Forever, and Beyond Good & Evil 2 (the latter has somehow passed the former's record for longest recognised game development time at 20 years compared to 14).
Super Mario Bros X is arguably getting up there too, started in 2009 by Terraria developer Redigit, and now in development by a new group as of 2026.
And while a Doom fan needs to check this, I remember the mod Mordeth started before Duke Nukem Forever was announced, and the later episodes ain't done as of 2026.
I'm reminded of an old talk by Rich Hickey [1] (he created Closure, initially in semi-isolation over some years).
[1] https://www.youtube.com/watch?v=f84n5oFoZBcSoftware
Richard Stallman: GCC and Emacs - both massive pro?ects and still going strong.
Linus Torvalds: Linux OS kernel
Science
Geoffrey Hinton: scaling neural networks
Books
Donald E. Knuth: Structure and Interpretation of Computer Programs (vol 4c of 12)
Buildings
misc. architects and builders: (most) cathedrals (Cologne, Barcelona, ...)
I think Charles Babbage is a special case -- IIRC his son also picked up his work, after his death. So he actually worked on it for "generations", by having a child who also worked on his ideas :-)
Darwin took 21 years to publish his findings on evolution. In fact he couldn't finish the actual book that he had set out to write and published a summarized abstract instead, which is what we know as On the Origin of Species.
Plus he would have kept working on it until Alfred Wallace wrote him a letter about coming up with his own idea independently so it was publish together or get beat to the punch.
Don't most researchers fall into this category?
People who...
Ted Nelson!
Myself, Roger Wagner,HyperStudio, 1988...1998...2008+
I guess Chris Roberts and Star Citizen will join that club
A couple software examples off the top of my head are Richard Hipp with SQLite and Matthew Ahrens with ZFS. Both almost incomprehensibly sophisticated projects executed well over decades.
Neither are anything like a solo effort in the way these examples are, and it's hard to say what they'd be like without the long individual involvement.
In fantasy:
J R R Tolkien
Janny Wurts
M A R Barker
Ed Greenwood
Yes?
Growing up in a retirement community you would be foolish to ignore the fact that some things don't start getting good for the first few decades.
Most everybody else doesn't have such overwhelming examples, and fail to realize it until much later in life, if ever.
the title kind of implies there would be more than just 2