Collets on Faro's and other quick change handpieces wear out.
Simple as that. It's usual, and depending on how much and how you use
it will determine in part, how long a given collet lasts. A new
handpiece doesn't get you a more durable collet, but it does get you
all the rest of the parts, bearings change levers, springs, etc. Buy
the new handpiece when the old one is getting too sloppy in areas
Other than the collet.
Your run on foot pedal might well be contributing to handpiece wear,
if your not letting the handpiece stop before opening the quick
change lever. The faros do not but ball bearings in the change lever
mechanism, so if the shaft is still turning, then the lever acts as a
break, and that will wear down that little cam inside that's doing
the changing. And if the collet is still turning when you pull out
or insert a bur, then the bur is increasing wear on the collet.
And no, you're not the only one to whome this occurs.