IME, some polys continue to drop tension and trampoline more while others go dead and/or lock up, losing power. I found the ideal situation for me was to use a hybrid with one of each. With the right combo, they can offset each other's aging issues pretty effectively.
I ended up with ALU Power Spin in the mains and regular ALU Power Silver in the crosses in my PA. Although the feel did change over time, playability, power, and trampolining were really pretty consistent until the texture wore off the mains. I did have to string it on the tighter side (#56) for control because the PA pattern is so open. A similar, cheaper combo is Tour Bite or HyperG mains with Pro Line II crosses.
If I were still using the PA, I would also definitely try Kirschbaum MP Rough 17 in the mains and regular MP 17 in the crosses. MP are prestretched strings that offer a firm but not harsh feel with minimal trampolining, good spin, and great control. For me, MP retains its playability longer than any other poly I've tried except for Head Hawk, and I've tried a lot.
Just be aware that MP is a very heavy string and will add 4-6 points to the swingweight compared to most other similar gauge polys. If it's an issue, you can always use MP 18, which offers a little softer feel and more spin without sacrificing much control or string life.