Jason Dyer has a blog called All the Adventures (via RPS) where he plans to play and write about every text adventure ever made, from the beginning. It is of course a gloriously doomed undertaking, just like the CRPG Addict's impossible quest to finish every CRPG in chronological order, which is why it's wonderful. Right now, Dyer is playing and blogging about Ferret, an obscure sci-fi adventure first released in 1982.
The original Ferret was made for the Data General Nova, a 16-bit minicomputer, and was only made available for PC with a DOS version released as a free download by the original authors in 2009. Ferret's anonymous creators, who worked at the UK division of Data General, explain that since their game was "Developed in stages, the game's architecture allowed the addition of extra phases in an incremental manner." And so they continued developing it, the updates ending with a "Final functional release with end game" that was uploaded on August 15, 2022.
That means it was 40 years between the first version of Ferret and one with an end game, which may technically be a record for "longest time a game has been in development". Good luck beating that, Beyond Good and Evil 2.
As Dyer points out, Ferret has 3,449 objects and 1,785 rooms (though not all of them can be reached by the player). For comparison's sake, the original Zork has 60 objects and 110 rooms, while A Mind Forever Voyaging has 30 objects and 178 rooms. Ferret may not have as many words as Cragne Manor (a collaborative work made by 84 designers), but it's a big game. And one that's going to take a while for any player to finish. It's an old-fashioned game of trial-and-error puzzles where you usually find out you've made an error by dying.
If you're still interested in trying Ferret for yourself, be aware that Windows does not like the official download and will flag it as a trojan. Fortunately, Dyer has made a minimal download available that will not make Windows have a conniption fit. After downloading those files, you'll want to run ferret.bat since ferret.exe launches a version that closes the window immediately when you die. In ferret.bat you'll stay in the parser and be able to begin over by typing "ferret" to relaunch. Remember the "save [filename]" and "restore [filename]" commands are your friends, and good luck.