I don't get tired of my e-readers (Sony PRS-300, Android phone) due to reading on them too much. But as a nerd at heart, I do get bit by the "new gadget" bug every now and then - absolutely!
But so far, I've resisted. I've only done two upgrades - one to a PRS-300 when Sony trashed my old PRS-500 in the process of "upgrading" the firmware for ePub, and the other to my new Android phone instead of my old iPaq PDA, since the phone does everything my old PDA did, and makes calls (sort of) too.
With that said, I've bought e-readers for husband, son, dad, and one of my girlfriends, and so I've still gotten to indulge that "new gadget" bug a bit