I started out 12 years ago with the now discontinued HRC215's. Got several years out of a pair of those. Have used HRC216's since then. I always mulch-mow. A year or so ago I had a drive shaft failure, switched to my backup and had the same failure on it the next day. But these mowers were 5 years old. I might average 5 cuts a day, which maybe is not as heavy use as some people put on these.
I later had a drive shaft failure on my newer HRC216 a year ago, after 2 years of use. So it does happen, but has not been a huge problem. Also it is not too hard to learn how to replace these.