Walkthroughs for custom maps.

Detailed information about extreme experience point values, including the causes of the bug (numerical overflow) and what will happen if a hero of level 75 or higher visits the tree of knowledge, can be found in the Physics and Mathematics Guide, in Russian. It also contains a complete table correlating levels and experience points.
Personally, I have never reached dangerous experience values and have not encountered such problems. However, I would advise that an overly powerful hero should not strive to gain more experience and should only fight when necessary.