I've got 26K on some Bridgestone Duelers. Not my first choice, came with the car. Was really planning to push it one more season on what's left of them. I rotated them regularly, but they really do look thin for bad weather use. Totally street legal though. Noticed a nail in one awhile back. Now it is losing air about every 4-6 weeks. Dealer said they couldn't patch it because it was too close to the sidewall (just past the first groove in the tread). But, the manager told me he honestly thought any tire place would be able to patch it fine and said I should do that since there is plenty of tread left.
I'm of a wait and see mode now. A great sale, or if it starts losing air faster I'll do something about it. Otherwise just keep driving. Fact is many many vehicle tires have nails and screws that go un noticed for the entire life of the tire. However, knowing about one makes a person paranoid and for good reason!
Anyway, I'll probably get new shoes before any really long trips. Got fix a flat cans, a small compressor, and a spare of course should my risk not pay off before then.