Sanoy eneloop appears to handle storage pretty well. I did a small search and it appears that their claim of 80% after one year has been verified by independent testers. But the higher the temperature the more rapid self discharge. Cool is good.

One option for eneloops is to rotate sanoy eneloops between your every day usage pool of freshly charged batteries and your emergency storage. Say every 3rd or 6th month, or every year.

Also, buy a digital multi meter (voltage meter) and / or a battery tester. The best test to measure capacity is to measure voltage under load (which a good battery tester will do for you). But as far as I understand there is no fail safe way of telling 100% good alkaline batteries from crappy ones - if it's unused it can apparently have a high voltage.

For alkaline storage: Keep 'em cool. Handle with care - don't toss them about. Never mix batteries of different brands or different charge levels in a multi cell application. (Once the weakest alkaline is drained the current is reversed => instant leak. The device may actually still work if the other batteries are good and the device can operate at lower voltages). I don't know how long you can store them - batteries are less prone to leakage now than before, but it still happens. Apparently, good alkalines can be stored for several years, but if you're unlucky you will have a leak in just months. There is an expiration date, but I don't know if that is of any help. Never store alkaline batteries in the apparatus!