I usually play at most half an hour in the evening while listening to a post being read on PeakD or a video. It can be less, depending on how much I up the speed or if I get my ass kicked before finishing the full waves (including bonus round), and if I still have solo quests to complete or not (right now I still have them since I recently unlocked League 4). To me it seems more relaxing than ranked play in Splinterlands, but I guess it's a matter of preference.

I don't think it's late to start in SoulKeep. It is much like Splinterlands early days, but a different genre.