serpentine belt

My '00 GMC Jimmy SLE only has 25,6XX miles on it. The dealer told me the serpentine belt has multiple cracks and needed to be replaced. They replaced it, but are those belts suppose to last for approx. 60,000 miles. I'm thinking I just got ripped off!

Number one rule of the game, "Keep your used parts" and make them show you the problem while your part is still on the vehicle ( not always possible with all parts) As sometimes unscrupulous places will show you any old belt and just tell you its yours.
Take the old belt bend it backwards in between two fingers see any cracks ? No ?
You just got snookered !! Better yet, invest in a service manual even if you can't do the work yourself, you'll at least know the basics, and you'll be surprised how much you can do yourself.
Good Luck

When you are talking about rubber parts, you must take in account time.......rubber will dry rot over time.
Your vehicle is 3 years old and from the mileage, you drive less than 10000 miles a year..so if you waited to 60000 miles to replace the belt, it would be almost 7 years old.....
In comparision, I own a 02 GMC with 55000 miles on it and my belts look like new.....

Merlin is 100% correct, the lifetime of rubber stuff like belts and hoses cannot be rated by just mileage, as this stuff lasts pretty well here in the soggy end of the country, but doesn't last at all in the hotter drier climates.