308 / 328 / 348 T-Belt change interval, what's the real deal?

I ran my last set of belts for 40,000 miles, 4 1/2 years and they looked good when removed. That was on my mecanic's advice for a 77 308. According to him, when Ferrari went to the QV and put the belts inside, they found they had to develop a more durable belt for the QV. That more durable belt gets used on all 308's now, and so they can run 30000 - 40000 miles reliably on a pre-QV car. IF you don't go too many years....

 

Earlier today I drove a neighbor's 1981 308i with 28,000 miles, original tires (sad) and belts. I advised her of the need to do the belts.

I also told her that the car would drive better on new tires, even if she has to stay with the TRX's (TireRack's got 'em for $209 in stock). Her car isn't in bad shape, it just needs to be driven more!