I generally go from contract to contract, so about 2 years each. Usually get the latest greatest Moto or HTC available as soon as my 24 months is over, but the flagships are so good now and so little changes from year to year, I was thinking of saving some money this time and getting an HTC One M8 (instead of the M9) as I can now get it for free on 2 year contract. That means I'll have it for two years, but it will be a 3 year old phone when I replace it.