It's to my understanding that you can simply go to jail to decrease major skills. I'm not sure what the max is, but the higher your level, the more overpowered NPCs and boss monsters are. Even daedric weapons and armor seem useless. Powerful spells do minimal damage. Because leveled equipment officially stop getting stronger at level 30, and how powerful your character is is proportional to how strong other NPCs are, it's probably smarter to stop leveling past 30, even lower than that if you specialize in a single fighting style.
I've managed to max out every attribute aside from personality and luck at mid-20s. Because increasing remaining attributes and maximum health (which is why it's important to max out endurance asap) are the only true benefits to leveling after level 30, what is the value to power leveling? I consider my odds less in my favor at higher levels because that means NPCs are catching up their attributes and will eventually be even with me. Also, what is the highest level character you have worked on?