[Andreas]

The increase in the power of your Allies is an issue for all kinds of Learning on the Job and unlike Recover Energy, most other skills don't stop giving benefits like that. Remember that you "may claim a maximum of eight hours on the job per day", so Recover Energy on the job learning comes at the expense of being able to do such learning for other skills. If you still find that problematic, you might want to change, or stop using those learning rules for all skills.

As for how many hours per day it should count for, that would reasonably depend on how much time the mage spends casting the spell in question, or if you don't want to track that, however much the player wants it to count for.