Belt stretch or a faulty tensioner?

[Zombietime]

I put on a smaller belt for my smog delete car... i first had a 85.5 which was too big, so i put on a 85 which got the tensioner back inbetween the arrows but now the tensioner is back where it was. I assume i need a smaller belt still but am wondering if these tensioners tend to wear out with age?

 

[Kiknads]

the only thing I've ever seen wear out on the tensioner is the pully bearings, although I have seen a spring crack, but you would definately notice that

 

[The Shape]

Zombietime my belt does the same thing. I put on an 85" belt and it will be right inbetween the arrows. After about two days it is right back out of range. Mine has been like that a couple of years now with no problems. If I try to go shorter to an 84.5" belt my engine surges on start up really bad like the belt is too tight. I would just keep a watch on the belt a few days and if your engine is satying cool and your alt. is charging and you hear no belt squeal I wouldn't worry.