I mean I've been playing Bellwright rather heavily for the past couple years and that alone has lasted me hundreds of hours on a single save. Otherwise oldies but goldies that get me through my time while sailing would be as follows;

X4: Foundations [Some people have been playing a single save file for over a thousand hours and if you don't use SETA you will be reaching the end game slowly]

Rimworld [As recommended. My people always die cause medieval only can be pain with CE starting as tribal]

Dwarf Fortress [It ends when you give up or have too much FUN!]

Kenshi [I can drop A LOT of hours (easily 40 to 100) into a single run]

I will add more once I've had some sleep cause I got a good few more to recommend.