I'd still change it at 50K. Sooner or later you're going to sell the car and regular maintenance is what someone who buys an older volvo is going to be looking for. You should also have changed the tensioner at the second belt change. Try spinning a new tensioner bearing by hand vs your old one.

I once soaked an old tensioner in amsoil synthetic engine oil for a week...it really smoothed it out. Used the wheel for 30K and changed it out with a new one at 140K on the 87 760T when I had to put a new timing belt on when the cam seal leaked. The soaked bearing appeared still serviceable, but put a new one on anyway. I wonder how long the stock bearing would last if it was originally loaded with synthetic lubricant...something volvo didn't specify!!!