I've had the dreaded S-bulge happen on some major name brand tires. One was on a Vittoria that I'd only had about 1 month, and it developed at mile 80 of a century.

I'll admit that I don't like to spend big bucks on tires, but tire quality is a bit of a gamble these days. I've never had S-bulges develop until the last 5 years or so and I've been road riding since the '80s.