I think we've already built up enough of an intellect fortress not to be worried.
Seriously, does anyone know of a French-language forum that could help le Redoutable? My Google-fu
c'est tres mal.
I
think he's saying you should need less XP to go up each additional level, because you get better at doing something as you practice it for a living. I can't say I agree; it's harder to learn, say, physics if you don't know any, but at a certain point it gets harder to proceed as you enter areas that haven't been studied or are more challenging. It's less trouble to learn electromagnetism once you know Newton's laws and are comfortable manipulating equations, but doing original research is going to get harder the more esoteric you get. Similarly, it's hard to learn to box, but once you do it's easier to learn new techniques...but you'll probably never be good enough to go up against Anthony Joshua or Tyson Fury.
The reason nobody does this is because monsters get more powerful, so the further you go along the more XP you get for each one. The problems with balancing this over the years have led to a lot of DMs giving up and levelling people up at given points in the story.