I bought my first iMac in 2008 and am about to upgrade for the first time. Well, hopefully. Not sure what's taking so long for the next iMac to be released. I'm guessing I'll be upgrading every 4-5 years. I usually upgrade my iPhone every 2 years. I'm thinking I'll do the same with my iPad. I purchased the iPad 1 about 6 months after it came out and bought a used Ipad 2 when the 3 came out. I'm not sure if I'll keep buying the previous model every two years though. I may take the plunge for the 4 if it seems worth it then get back on the 2 year schedule.