What alvin describes is what happened to my lamp over time (NEC, not Panny, but have heard similar stories about other brands). Ultimately we all have to replace lamps, some sooner than others (no. of hours is not consistent even with the same pj). Didn't want to start a new thread, so I'll just post this here.
Some things I learned:
1. When turning your pj off, try not to turn it on before 60 mins. are up. Some put the threshold at 90 mins. just to be conservative. If you're going to be back within that time, it's better to leave the pj on.
2. Try to plug the pj into a UPS esp. if your area is brownout-prone. It's the sudden turn-off and esp. sudden turn-on that can shorten lamp life significantly. Some very cautious owners only like higher-end UPS which output pure sine waves, but IME a regular APC is good enough.
3. Use your regular tv for watching special features.
4. Heat and humidity and dust - try to minimize these. Anyway for light control you'll usually have A/C on, right. Occasional vacuuming can help, even if your room is sealed.
5. Try not to put your pj into high-brightness mode. Try to use the other adjustments as the lamp life gets shorter.
6. If you're planning a trip to HK (or maybe Sing), scout in advance for where you can buy a replacement lamp, from the distributor if possible. Will cost much less than buying it here.
7. Get a high-gain screen.
Hope this helps. Good luck on your lamplife guys