Overnight accelerometer usage I use the Sleep Cycle app almost every night, but am concerned about the "health" of the accelerometer in the phone. For the app to work, I set a time frame for it to wake me up, then I lay it on the mattress (not under anything to protect from heat buildup - I've never felt it get warm), and it uses the accelerometer in the phone to track my movement. Nice idea.

Does this kind of 7+ hour per night wear matter?
No. weather you're taking readings or not from the accelerometer or not, the components inside still move around the same way.

For more information on how accelerometers work, check out this insightful, easy to understand by the engineerguyvideos channel on youtube.