Slipways is not very content-driven, being more of a replay-based game with 1h-long runs (with each run featuring different content when it comes to eg. technologies). It should take you about 10 hours to see all of the technologies, perks and then go through the campaign, but it all boils down to whether you like the style of gameplay the game offers. Right now, the average "time played" on Steam is a little over 12h, with quite a few hardcore players having 100h+.