“Long” is a relative term too, due to the number of hours you put in a single period of time.
I started work on Six Silver Bullets sometime in 2002-2004, and didn’t finish it until 2018…but that’s because I spent huge periods of time not working at it all (and often starting and restarting it). All told I spent ~300 hours on the iteration that ultimately got submitted to IFComp. It has ~30 locations and a few hundred special actions.
I started work on Skybreak! in 2017 and finished it in 2019…but I worked on it almost every single day. All told I spend ~700 hours on it. It has ~300 locations and thousands of special actions.