HTC M9 suddenly changed vibration strength?

[Android Central Question]

My phone (HTC One M9) used to have a good medium-strength vibration. But suddenly, it has started to vibrate much more forcefully and violently. Might this have something to do with the fact that I let it ring for about fifteen minutes, thinking it was someone else's phone? (It was a four-way hangouts conference, it rings until everyone hangs up.) Surely my phone, for the time I've had it, has rung for more than fifteen minutes in total before that... that alone wouldn't wear out the vibration motor, would it?