You should check that more closely.

NiMh lose a bunch starting as soon as they are disconnected it from the charger.
Stored at 70 degrees F (20 C) NiMH batteries will lose up to 40% of their charge within a month.

They also don't handle higher discharge as well as NiCd. And they shouldn't be charged at the higher rates NiCd can handle.

The best technique is to charge them the night before you're going flying.