What is your experience with moving an existing character?
I think that there are two things going on when people want to move characters, that are almost unrelated.
1. For Pathfinder, especially, creating a character is so much freaking work, given the interaction between archetypes, skills, talents, special talents, feats, spells, etc. If you put together a character with a particular synergy of these elements, and then the game dies in the first few months as often happens, I can see wanting to reuse the character. You just want to see if you get the interesting synergy that you were hoping for.
2. I have a particular character, Aduz Agave, that I have started in at least four different games now, on different systems, and have yet to explore his personality fully with a GM that really enables it. The longest a game with him has lasted was barely over a year; and that was a slow-paced game, so the equivalent of just 4 months in a faster game. I really like this character for his quirks and humor, not for anything in particular in the game system, and I'd really like to see him mature. For instance, he has a pet warthog which he has named "Dog," which makes him guffaw every time he explains it to anyone. ("He's a PIG, named DOG. Do you get it? Hahahahaha!")