> So the generator is not being 'reverted' but rather never advanced?

no, because I get new values for new records from the generator. It is
being increemented then being reverted.

> I prefer to let the Firebird insert these values using a
> trigger.

me too...

> Ok as long as you don't need the value in other tables, but
> more of a problem if you need to use it as a key to records in
> detail tables.

I do on detail inserts.