Squealling Belt - Repeat offender

My 1999 Mazda 626 4cyl 130K miles, broke the serpentine belt for the Alt and WtrPmp at 125K. No squealling no nothing, just broke from mileage and wear (?). I replaced both belts due to the high mileage and "Murphy's Law of Auto Reapirs". Cost $40 and 2 hours of my time. About 3 weeks later the squeal is back. I can't identify and idler pulley in this blet path - Alt/WtrPmp/Main Pulley - so I tighten the belt slightly. No help, squeal continues periodicaly until the belt breaks again after about 45 days and 4K miles. Fearing workmanship issues (Me) I had the dealership do it the 2nd time. Both belts again, $213. Now after just 3 wks I'm back to square 1. I took it back, told them it is squealiing. They adjusted the belt slightly cleaned the pulleys (belt crud, imagine that?). They said everything looks fine. No mention of Idler/Tension Pulley. They didn't seem to have any issues with Alt or Water Pump. Alt makes no bearing noise, Water pump makes no noise. But I still have the squeal problem intermittent on start up and pulling away from a stop once in a while. Any thoughts? IS there an Idler Pulley in the Alt /WtrPmp belt line?