My PX200's are probably getting on to a year old, but I doubt they have more than 100-200 hours on them. I do use them fairly often for short periods when travelling, but they don't get used for very long periods... averaged out over the period I've had them it's probably about 15 minutes a day. And also to me they've been more or less always like this.
As I think I said on more than one occasion, my first pair had a very stiff last detent on both sides, making me believe they wouldn't extend further and the seal was constantly being broken (yes my head is that big)... which had a big hand in me disposing of it. The PXC250 and the PX100, both of which I bought later made me realise that there was one more detent I could use, and when I got the PX200 again by fully extending the headband I could get a good fit. Since then I've not been inclined to be overcritical of them.
They're good value. Dark and somewhat sloppy but they do work perfectly well for the money, give actual isolation nearly on a par with the EX71 and they fold flat. To me they're more tractable than the EX71 as I can simply throw them into a bag without the rituals of putting the earbuds in the case and also of course the reverse... blowing off little pieces of fluff off the EX71 buds, etc.