After a few weeks, I called my mechanic, since I had not received a bill.
(See previous threads for background):

Immediately after the last annual, the plane threw an alternator belt. We
went through three belts, and the last one has been in for six hours and
worked fine. During this time we had both voltage regulators pulled, along
with the alternator as well, due to electrical charging problems. Was
finally told the engine counterweight bearings were likely worn, and needed
replacing. This job would require pulling four cylinders, and cost nearly
$2,000.

Anyway, the most likely culprit was a bad alternator connection, which
appears to have fixed the problem.

Regardless, he told me there was no charge for the work, including the three
belts as well as the evaluation of the voltage regulators and alternator, in
addition to his time.

I was very pleasantly surprised, and said that if he thought it was fair, I
would be glad to pay for the testing and evaluation of the voltage
regulators and alternator, as well as the purchase of the new belts. I was
not looking for any freebies, and also understand that sometimes these
things happen, but it was not his fault. He accepted my offer.

In my opinion the integrity and commitment to customer satisfaction shown by
my mechanic are pretty unusual in this day and age. He showed pride in his
workmanship and stood by the job he did, and was willing to make it right.
This is not some guy doing ramp annuals- he has some big Hawker jets and
King Airs in his hangar that he also works on.

Who could ask for more service and commitment in any field?

He went a long way for my peace of mind, in knowing that he would do
whatever it took to make the job right.