In the That never happens! department, check this out:

Short story long; Towards the end of the riding season last year I noticed the battery was going bad. I'd only had it for two years, and wasn't sure exactly how old it was. Bike batteries rarely last more than 4 years.

Symptom 1: Once or twice I had stopped along the road and "barely" got the bike back running again. One morning the battery didn't start the bike at all and I had to roll it down the hill to get it started.

Symptom 2: Out in the parking lot at work I noticed my "red alternator" light came on and stayed on for at least 2-3 minutes. To my relief the light went out after about a mile or so of riding.

Planned Maintenance: I like to do my maintenance in pairs, so changing the battery is also a good time to renew the brushes and voltage regulator. I bought a new battery a few months ago, and just waiting for good weather to activate it. Also have spare voltage regulator/brush assembly from the parts bike, so was just now getting around to pulling the old brush assembly and this is what I found. Note one brush had come completely out of the holder but continued doing its job running sideways across the stator! Now, that's what I call a fault-tolerant design.