As a GM, the Pathfinder adventure paths are so freaking good, you can run them with minimal prep or adaption if you lack the time. Really well done. Still, if you want to adapt, you have a ton of stuff ready to be plugged in without breaking things. Also, the system works great at high levels, my group is lvl 14 and fights are still nailbiters most of the time (I sprinkle in the occasional easier encounter so my players can go crazy)