I've been through probably 5 or 6 MacBook Pros over the last few years, and I honestly no longer see the joy/benefit in doing so. Sure, that first week you have a little new tech envy, but it quickly goes away. Meanwhile you save yourself: the craigslist/ebay headaches, spending a couple (few) hundred extra dollars, re-insalling wrapsol and whatever else. My current machine does everything I need and more, and it's pointless to waste money, time, and effort simply to buy something for the sake of newness. Trust me.
The only way I'll sell and upgrade is if they change the body style completely again, and even then, I might not.
It's something that's totally up to you, just thought I'd offer my opinion as a former serial upgrader.
I agree with you 100% here I used to do the same thing with cellphones, I counted back 3-4 years, and I averaged about 3 months before selling the cellphone and buying another one, I jumped from Motorola milestone to nexus one to Iphone 4 in a span of 8 months. it was this constant "OCD'ing" of my devices, making sure it's placed on a napkin when on the table, making sure there's an invisible shield blah blah friggin blah, until it got to a point where I just stopped caring about all this stuff and just want to enjoy what i spent my money on.
Now I'm using an ip4, and I'm sticking with it for a minimum of 1 year before i dump this thing and jump onto a new device. Thankfully, I was never "infected" with this kind of obsession with laptops. I will like my battered and beat up laptop, It's got character