tensioner for sert. belt needed??

About 1000 miles ago (although that's more than a year because my truck
sits while I fly around the world) I was told (during a routine oil
change) by my
dodge dealer that I need a serp. belt for my dodge truck (about 80,000
miles). OK, do it...i said, without
looking at it. Now, during another oil change, the dealer (service
rep...a different guy and different techs) says "you need a serp. belt
and tensioner". WHAT? I you just sold me a S-belt 1000 miles ago. He
looks up my records and says..OK, "actually you just need a
tensioner, but the belt and tensioner are usually done as one job, but
you can just get the tensioner". I said I'm suspicious: didn't i need
a tensioner 1000 miles (one year) ago (in which case I would hardly
have to pay extra for it)? He didn't know. Did anyone check the
tensioner back then? He didn't know. So I ask you all: What is the
most likely scenario here. and how likely is it that I would need a
tensioner only 1000 after getting a new Serp. belt? I do know that
there is no noise at all or symptoms that I'm aware of. I think he
quoted
a price around $150. I don't necessarily trust the service dept.
because there is alot of turnover...new reps, etc. (p.s. How important
is this tensioner...does it just reduce the life of the S-belt if its
'bad'? ).

Yes and no...
The tensioner could have become weak or worn out. That would cause problems
with
the serpentine belt, over time.

I replaced both belt and tensioner myself. It isn't a big job, but if the
frigging dealership does it,
it could easily run to $150.

Haven't you learned yet about dealership prices and quality?