I've got a radio in my emergency kit with a pair of the older style L91's - the orangish gold / red ones from the 1990's - with a 2009 expiration date. It was in my car for several years, subjected to summer heat in an enclosed vehicle as well as winter temps occasionally below zero. They also have several hours of use on them. I can't tell how much life the have left, but they were still going strong when I tested them last week.
They are pretty amazing. I keep 24 L91 cells in an emergency kit in my basement. I used to have them on about an 18 month usage cycle - pull out and use the oldest, replacing them with a fresh pack. With the advent of LSD NiMH batteries, I find myself not using L91's quite as much, but the storage life and energy to weight ratio is hard to beat.