NiMH batteries have a worse self discharge than NiCad even. I've charged both and in a month the NiMH were too low to use and the NiCad were still useable until about 3 months. Rechargeables are great for things you use each day buy not great for storage. Lithium is the best for long term storage as they have a 10 year shelf life and they are great for BOB/PSK/Etc lits because of their lighter weight.