The battery in my current GPS bike computer, a Wahoo ELEMNT, has started failing. It never had an excessively long life, but it’s dropped to under seven hours. Most of the year that’s ample, but right now I’m doing extremely hilly rides that can take seven hours of moving time, plus stopped time.
When the ELEMNT dies, it doesn’t warn you — it just shuts off, and won’t turn back on again, come hell or high water. Then, when you get home and plug it in, it starts the ride up again, recording time and distance miles from where it died. Sometimes the route is corrupted, so you lose most of the ride data, too.