I've found that my Eneloop NiMH batteries need to be recharged every 4 months if not used. I thought they'd have a better shelf life.

Btw, I've completely stopped using standard alkaline AA's and AAA's due to leakage. Now only using NiMH and lithium batteries.

My Bosch hand tool NiMH batteries seem to have much better shelf life, but I still try to check them every 6 months or so.