They are spec'ed for 300 charge cycles , I have some that have been going well over a year ! , every once in a while I have had some that the protection PCB trips and the output goes to ZERO volts !! do NOT throw them away !!! let them sit for a few days then retest them , they tend to come back to life.
I had a couple 18650s I took the protection circuits off because they went bad. I used them for testing circuits and size requirements after that.
With the protection the Buzz has I wouldn't be afraid to use unprotected batteries in a pinch.