When I'm at the point that I have infinite resources, I always dig into other mods. Build massive power grids/stations. Attempt to gather all the bees, all the thaumcraft recipes/research, all the wood types, etc.. In unleashed I made a touchscreen mobfarm with all possible mobs to soulshard. All the mobs were gained legit. I eventually started up a twilight forest mob farm.. Then built a linking base in the twilight forest as well as the nether, the end, and a bee/tree world with mystcraft. I actually never finished doing stuff with it because I kept exploring new mods and making new goals. It would take hundreds, if not thousands, of hours of legit gameplay to get through all the mods and really achieve "everything."