I suppose we should also mention which pad we have, since you mentioned deterioration. I use Lake Country variable contact ( I am switching to the flat DA pads soon I think).
More importantly, I also spur my pads while polishing periodically. If you don't have a spur, you can use a plastic putty knife or similar object (metal may tear) and let the PC run for a couple seconds (speed 5-6). It should spin up to full speed then LIGHTLY with the "spur" angled away from the pad touch the pad and move outward in a slow spiral. You should see caked polish fly off in a tiny stream. Repeat until clean.
DO NOT angle the spur into the direction of rotation, you will gouge the pad and more importantly injure yourself!! Eye protection recommended.
Lightly mist with water and you're ready to go again!