Lots of good info above.
Personally I do NOT use Chinese tires at all, so not much comment on them. I admit IF I had some, I'd replace them. If you post the first few letters/numbers of the DOT code, we can tell you where tire were made, and by who. Note full DOT code usually only on one side of tire, and per Murphy it is the side under the TT.
I run TT tires for 7 years of age per DOT code, OR until I can stick a penny into the tread and see the top of Lincolns head. If I can see the top of his head, tires are worn out. This is true for car and TT tires.