As a side note, I've stopped calculating XP in our Scales of War game and just hand out the right amount of XP at significant plot points. It's made my life easier, and the players know they won't be penalized for coming up with clever monster-avoidance solutions.
We do something similar, but we found that we want to advance quicker during the lower levels, and advance slower during the mid and higher levels. Character personality is created most at lower levels, where you need to be more creative to get things done. But there is much less you can do, so we want to move through them quicker. Once we gain power, then things are slowed down.
One other problem that we have resolved is unequal leveling. If someone misses a game or two, they start falling behind. We had one player who was a bit behind in XP and had to go away for a month. When he returned he was hesitant about rejoining the group over two levels behind the others in experience. When we told him that we changed to equal leveling for all characters, he changed his mind in a snap and was extremely enthusiastic about rejoining.