FWIW:

I've had Goodyear RSA's with bad belts that caused vibration.

I had the same problem with Good Year RSA's, but it was constant ... not just when veering one direction.

On my Park Avenue the 60+ mph vibration was fixed by the dealer re-balancing the tires. They had been previously balanced by a tire chain shop but apparently not closely enough. Easy peasy.

Speaking about wheel bearings: How long should one expect the wheel bearings to last?

I am hearing some sounds now that may be wheel bearings. The sounds are noticeable above about 45-50 mph. The car is a 1994 Buick Le Sabre with 91,000 miles on it. It is more noticeable at 65-70 mph. The tires are 3 years old with about 55k miles and are Pirelli P4s. There is still a lot of tread on all of the tires. They are guaranteed for 99 k but I don't think thaey will make that.

I understand that wheel bearings in these models are not serviceable but an R and R kind of job. Wheel bearings that you don't grease is a new idea to me.

It is interesting to read about the vibration issues with these cars. One thing I have noticed is that the chassis/body is not very rigid and wonder if that adds to the vibration issues.

wheel bearings make more of a vibration that you can feel, and will go away or vary greatly if turning or hitting the brakes. the tires make more of a howl like big mud tires and doesnt really go away so much when turning or braking

If the tires' treads have begun to harden with age, a tire might be causing the noise. If they haven't been rotated regularly, they may be more likely to give the noise, in my experience.

The only sure way is to rotate the tires front to back and see if the sound and noise changes. I tried the swerving test where on a sweeping curve at 35 mph turning to the left puts more load on the right front bearing and takes load off the left, and that would indicate the left bearing was suspect if the noise stopped. But my older Michelins quieted down on that test. A neighbor who had worked in a tire store before being a very competent shade tree mechanic felt the treads and said it was likely one of my front tires. I rotated front-back and the noise changed, quieted. The tire actually had bad belt according to Michelin selling store.

I actually replaced a front wheel bearing under warranty because I thought it was the bearing that was a year old.