Board Thread:General Discussion/@comment-110.146.149.161-20150813074512/@comment-25555436-20150903013343

Which is why I said before that an equal amount of effectiveness could be reached if Weiss simply trained her Aura to last more, or sort of be of a higher quantity.

If Spell A uses 15 MP, it would cost less than using Spell A and then B which combined would cost 25 MP. However, the MP cost difference is made unimportant if you simply increase your Max MP amount from 100 MP to 145 MP. You would still be using more MP than the alternative, but the higher MP amount means that the higher cost doesn't matter too much.