That is very interesting. I have a 4 year old G4 with it's original 2x A04 DVD burner still working and I have had one DVD (A05) Firewire burner go "funny" on me. I replaced it with a A09 Pioneer and it's all peachy.
The latest 110D from Pioneer can be had some days for $45.00 so replacing it every year shouldn'e be a big thing. You must burn a LOT of media with your DVD burners.
As for the BluRay and HD-DVD; we don't even know yet when they will appear and most likely, just as the original Superdrive was, it will probable cost $999.00.