Worn out rim tape. Is 12 years too long to have the same rim tape? There were no sharp edges, but my little LBS guy said that the indentations were deep enough to make a tube blow under 120 lbs of pressure.

This is a tiny little shop - think of Andy Griffith's barber shop - that's it. Older guy & his younger wife run it. Gave me a few bits of info:

He said that putting corn starch on tubes to make them slip in is NOT a good idea because you don't want the tube moving inside of the tire & bending the valve around.

He said Continentals are the last pure rubber tire. Soft, good for gripping the road, most perfectly round tire, but they don't last very long. (I don't care, I have an aversion to road rash.)

He said small shops like his can't compete with Performance, the internet, etc., and soon we'll all be shopping at big box stores. I hate that. The worst repairs I've ever had were at those stores.