I added a air stone to my tank about 4 weels ago.
In the begining the bubbles came out of the whole bar
but slowly less and less, and now the bubbles
only come out of the end that's closest to where
it's hooked up from.

I have a bare bottom tank, and took the stone out
to clean it. I even brushed it's surface with a soft tooth
brush.

Do these things just ware out that fast?

I had a 4 inch airstone for 5 years. it lasted forever. What kind of air pump do you have, and do you have a bleader valve?

mine is 4" also, yes I have a B valve and an Aquatice Gardens air pump 1000

mine gets a little less every once in a while too, I just turn the airpump up higher every time, maybe the vavlve on mine keeps closing somehow