Once you've researched everything and found the end game goal, only thing left is build bigger and better raft. Currently anyway. If you're not into base building, you probably go through available content pretty fast. For people who like to build, content lasts as long as they don't tire of it (remember all those gigantic building projects on Minecraft like 1on1 model of enterprise or working computer in game or hundreds of other massive things people build with it).