That's been my experience too. The first set of AW IMR's I got for my grand "seemed" to not hold a charge as long as when I got them, so I treated myself to a new set. But keeping the old set around "just in case", I periodically recharge them so they'll be ready to go. At first I recharged them every month, but my battery meter told me the same thing, and what I'm seeing now, is that they barely lose a measurable charge over at least 3 months...I'm tempted to start topping them off every 4 months.
These "spares" sit in my bedroom (temperature controlled environment), so if you carry them out and about (especially in cold weather) you may not find the same, but I suspect even exposing them to (not TOO) cold temps, they'll hold a usable charge for a good 3 months.
