More like 6.66666 months (200 days is the average update cycle) and I keep my MBP as long as it works.
My last laptop, a Thinkpad (IBM - not Lenovo) lasted 7 years, I'll be lucky to get that out of this uMBP but I was thinking about 5 years?
I have had mine for about a year. I bought a 27" i7 and I was going to sell the mbp but I couldn't get an i7 that didn't have issues so I have kind of decided to keep with laptops and externals. I will probably get a new one next year maybe?
Agreed, notebook collecting is indeed an expensive hobby. However, I am always intrigued by performance upgrades, but my inner-miser kicks in and I purchase a new Mac every 2 years or so.