Recently swapped them out for iridium ones. Driven about 500km since then. My hemi loves them and I dont have to bust my knuckles for another 160k km. A good thing!!!
The XP's are ~iridium~, (Iridium enhanced), BUT, they are marketed as a Performance plug,,, not necessarily a long life plug,,, (The ground strap is tapered and has no 'precious metal' puck welded to it.)
Plug wear will vary from engine to engine, but the ground strap may erode before you reach 160k km,,, (I had the XP's in a '00 Chebby that were eroded pretty bad after 50k miles)
With that being said, I ran the XP's in my 09 RAM 5.7 The 09 had about 45K miles on the XP's when I traded it in and ran smooth as buttah,,, I also have a new set of XP's ready to go in the 14,,,
IMHO, If you get the XP's with a rebate, you really can't beat the 'bang for the buck',,,,