>From the response of people here, I believe my fear is irrational. The fear comes from knowing that there is no way to generate any unused values should the counter somehow skip ahead. I don't know how it would skip ahead; perhaps bug in my program(?).

You can try to insert a record in a transaction, then rollback. My guess is that the counter would revert together with the transaction.

If you add two records and then delete the first one, its number looks unused, skipped if you want, but it was used while the record existed. So skipping seems to depend on the definition of "used".