Start of season problems hit everything -- why do you think it takes twice as long to get a bike serviced at your LBS in early spring than early winter? Batteries that have been getting weak just don't work after sitting for months.
As far as I can tell, the average life of a blinking taillight in normal circumstances is about 2-3 winters' of commuting. Didn't have one fail last winter? Might be because I was WFH all winter, they may last through this winter too.