when I did the service on my WRX, I was at about 8.5 years but under 70K miles.
the toothed idler and another idler spun like like skate wheels, the toothed idler also wobbled slightly. There was oil on top of my tensioner. Belt looked surprisingly good. No signs of seeping oil from crank or cam seals.
I left the waterpump but changed the belt ,tensioner and all idlers.