The third time someone calls to complain that the alkaline batteries they put in this leaked, they'll wish they used a soldered-in 3V lithium primary cell. Even though that goes against a certain ethos.
The lithium AA/AAA/CR batteries don't seem to leak. They're not widely available though. I use them for devices which mostly sit in a drawer and their lifetime can reach 5-6 years.
Tracking weather balloons. They use lithium AAs for power, and the mission only uses a fraction of their capacity. When the balloon pops and the payload lands, there's a good pair of AA's laying in some farmer's field, stuck in a tree, or otherwise sitting around waiting for you to clean 'em up.