Are you absolutely sure you installed the new belt correctly and that it wasn't damaged?
What type of belt did you take off and what did you use to replace it with? Part numbers?
The reason I ask, I've seen this happen before on another Chrysler vehicle.
I have a 2000 Dodge Grand Caravan and when it came time to replace the belt, I bought a typical replacement from a local auto shop. 3 weeks later, the belt shredded. I took it back and they replaced it. That one shredded 3 hours after installing it. I took it back, got a different brand. It shredded in 5 days. Got another one, but the belt squealed.
I put it on a shop, had the idler pulley and tensioner changed. same thing.
I removed the alternator and had it checked. Everyone was telling me to change the belt, it was bad. How can that be? It's brand new? And it keeps breaking belts!
So, after having to go get my wife on the road a few more times, I decided to change the TYPE of belt.
That solved my problem, no more breaking. I did some research and found this to be not all that unusual with those vans, and that Chrysler actually did a recall on the years BEFORE my vehicle for the exact same thing! Mine was effected, but not included. It even baffled the techs at the dealership.
Now, The belt I got was a Dayco brand Poly COG type. Nothing else would work.
But, and here's the kicker, Dayco no longer makes that belt. They make that same part number, but it's not a poly COG, it's a poly RIB. Big difference.
Why the hell someone would give something different the same PN is beyond me.
Point being, you could go around in circles, check to see if a poly COG will work or if that's what you are using.