Someone said this earlier but I think a fair time to keep a phone is until the next big OS change. So until QNX is on phones....which means until 2015 lol.
Everytime I buy a new BlackBerry, I always tell myself I'm holding on to it for the next 2+ years, but end up getting a new one every 12-18 months. I know people who have used their Bold 9000 going on 3 years and still dedicated to their phone! I'm buying the Bold 9900 at full retail price and want to make the most out of it. I will definitely keep this one for 2+ years (or until the QNX based devices come out).
Posted from my CrackBerry at wapforums.crackberry.com
I bought my 9700 on release and I am still using it today. I'll probably hold onto the 9900 until QNX comes out on bb's.