I purchased my first windows phone (omnia sgh-i677) in 2012, when I traveled for Manaus City in Brazil, now on march purchased my Lumia 920 when the Nokia released in Brazil.
Around 2-3 years. But if the device still meets my needs I'll try and get more out of it. I usually buy my phones sim free since I'm not on contract, so gotta make the most of it :wink: