My sense of operating temps for green lasers is that they are fine above say 5-7 deg C. As their temp starts to drop below that, they fade away. Many people blame their batteries but it's more likely the laser itself. Mine stays in my top pocket when it's not switched on benefiting from the exothermic metabolism in the lump of meat beside it.
My relatively cheap 5mW has performed well for some time. Lately it has been a bit sluggish to come up to full brightness on switch on - nothing a good thump doesn't fix - I'd better check the battery contacts
