I drive a ‘97 GMC Safari with a 4.3L V6. The accessory drive belt squeals. I replace the belt and not long after, it’ll begin squealing again. The service interval on those belts is long, if I’m not mistaken, and the current belt has fewer than 10k miles on it. I’ve stayed away from belt dressing products, but I find that spraying silicone on the grooved side of the belt will buy me a few weeks of silence. A new belt is less than $30 — I always buy AC Delco Professional — and replacing it is not the biggest hassle in the world, but I just replaced it less than a year ago.