I don't think I will attempt to change mine unless I notice a real drop in mpg or in performance, how smooth the car runs etc.
Let me guess though, did you have to take apart half of the top of the engine to get at them, as usual in modern made cars these days? lol I sure wish changing plugs was as easy as it was back in the day, when you had like a foot of space between the engine and the engine bay walls, and there was nothing even close to the plugs except maybe a header or something, these new ones sure can be a pain. I had an Impala that you had to ratchet and rock the engine forward to get at the rear 3 plugs ... fun times indeed! lol
Thanks all. Yeah the V6 requires partial engine disassembly. One reputable local shop has quoted ~$100 labor for the job. Pretty fair, but a royal PITA. As to the life, I'd guess that mfrs have to certify plug life for emissions compliance to the EPA. No? But it may be BS nonetheless.