I have seen some battery holders that attach to your key chain so you always have a spare set, just in case.
Since you should avoid keeping them in hot places like car glove boxes, what about your jean pockets? I assume this would not be a real problem for the ladies as they probably keep their keys in their purse.
Keeping a spare set around sounds like a good idea, but not if they are going to rapidly die any way.
Boliver