Wheel Bearing Went Bad...how Fast Does It Take To Go Bad?

[Buddy67Lincoln]

I have a 2006 GMC Sierra and one wheel bearing went bad at 12,000 miles! The other at 35,500! Just before warranty is up. Anyways I started feeling a pull probably last oil change at 33,000. I had the brakes check since it was almost up for warranty and one looks bad (the right front). They check in Meadville PA and say its the fine. I take it and the very next day I hear a squeal grind noise. I had it back in Pittsbugh for wheel isssues and asked them to check the brake since its making noise. They say its the metallic in pads and its normal. Sounds horrible by the way and not at all 'normal'. I drive an 04 Silverado with 40,000 miles and its fine. I bring it back up after getting the wheels fixed up and take it for inspection at 35,700 miles. It fails due to right front bearing being bad. I run it back to Meadville and they fix it same day. Not sure if the noise is gone since it pouring out right now but I asked them why did not catch it when it was in 2 weeks before??? I paid to have the brakes checked and they did not even tell me they were going to. I just wanted the multi point inspection done. You would think that since they had the wheel off that they would have just wiggled the wheel? They said it went bad over night. Meanwhile it was at 2 GM dealers and neithe caught it? I know that GM might have said brush it off since its almost out of warranty but they did not know I would have it inspected 200 miles before warranty is up. Am I wrong to think it has been bad for a while??? Or do they go bad over night. I feel like I was almost hosed! Let me know if I am wrong. Thought I'd ask you guys. Thanks for the help.