Plextor PX-712A Slowly dying?

I’ve had my burner now for 16 months, and totally satisfied with it. I must have burnt over 600 dvd/cd.
But Today i bought a bunch of prodisc cd’s and it won’t recognize them. I tried them on my other drive (LG), and no problem.Then i tried to clone a Dvd i had, and got errors, but when i did the same in my LG drive, it worked fine.
Is 600 about the max u can expect to burn before things start to wear out?
I have tried cleaning with canned air.
I ran all the tests using plextools, with good results.
Could it be just a conflict between prodisc and plextor?
I have the latest firmware update.

Get yourself recommended media (Prodisc isn’t) and run the self-test as being described in the FAQ.