2003 jtd with good service history. Just had to have new fan belt and tensioner. Same thing March 2014, approx. 9-10k miles. Has anyone else had belt last so short a time? Should I expect there to be a manufacturers warranty? Any thoughts folks?

I think the normal change interval for an auxiliary belt is about 3 years. A short life has a cause that needs to be identified.

Being a diesel, it is likely to have a freewheeling pulley on the alternator. Check this. If it is not freewheeling properly it can cause the alternator belt to wear quickly or to pop off. Search for similar threads on the Multipla section. Pulley is replaceable, have a look on Ebay, but measure its diameter and number of splines first to identify the correct one.