Well, I have ripped normal tires to shreds in less than a year due to my rather aggressive driving style. You could get cord separation and the tires still look fine. Another thing I would check is the universal joints. If it's a pulsing vibration at highway speeds (speeds up, slows down during constant speed), it is usually a driveline issue like the U joints or a broken transmission mount. To check these things, you will need to support the axle up on stands, put the car in neutral and go under the car. Look at the joints and spin the driveshaft. it should rotate smoothly. I would also give it the wiggle test to be sure they are tight. Then, look at the bearing caps. Are they straight? I once had a U joint that passed these tests, but the cross was half ground away and it had no bearings left! I found it by looking at the caps.
Now, if it is a "fine" vibration (high frequency) that you can feel through the wheel, it may be the front wheel bearings. When was the last time they were serviced? If it is the wheel bearings, it will not shake the wheel, but rather feel like holding the handle of a weed eater or lawnmower at high speed, only a little less pronounced. It may also make a faint humming noise.
Other things it could be: Bad alignment, loose transmission to engine block bolts. If the transmission has been rebuilt recently, I would suspect that. Also, do the "wheel spin test". Spin each wheel while the car is jacked up and note if it has any high spots or wobbles. Look at the tread surface, the wheel edge, and sidewalls. Some tires (cheaper brands) are not perfectly round, but they should not be very un-round either. There is a certain tolerance to tires beyond which you have issues, and these problems will be very visible.
