There is always the issue of what to do after reaching a certain power level.

To explain, on the site I would roleplay on before joining the Guild it was star wars themed. It started off very controlled, all gun slingers, smaller scale adventures. The power level slowly grew as they got more skilled, gain new friends and more tech. Eventually the force made it's way though, and that force starting growing very much like the Bell Curve Brovo mentioned.

This did last for a good few years mind you, but eventually when we finished our big plot we were left with nothing. We already did the biggest thing possible, saved the Galaxy. What else could we do? Save the Galaxy and it's cat? With smaller scale adventures now seeming more pointless cause if the lower power level that community ended up ultimately dying out after that epic moment.

Now, you could of considered this a successful roleplay ending since it did last a few years, but the main point being highlighted here is that we wanted to continue, but could find no real way or motivation to because the power level was so high, which is a common issue with high power levels.