From Letter VIII:

2:04:44
Q: I heard that you can reallocate your attribute points, but will this be something you can do easily multiple times?
A: You'll be able to use a special item you can obtain by exchanging a certain amount of another item, but it won't be something you can do so easily. For example, it's not like you will be able to allocate them so today you can challenge the Great Labyrinth of Bahamut as scholar, and tomorrow allocate them so you can go as summoner.