Dear Walt,
That is a nifty tip with the topstrap and pencil. I was under the impression that it was gasses that cut into the topstrap as well. If you know of anywhere that I can read about this, please point me in that direction.
Forgive me for speaking off topic, I don't have any experience with the 629's durability; but I would be surprised if it had a major malfunction during your life. I read an interesting article once that stated the cylinder always failed first. Of course they were talking about Ruger revolvers, but I imagine the principle still applies.
Take Care,
Rhyno