9? since 2005. I got my first cell phone before I went away to college. The first three were flip phones. Got my first smart phone in 2011, I think.
I usually try to get at least 2 years out of them. Sometimes I get more, sometimes I get less (one went through the washing machine at a few months old

, the battery life on my Samsung Note tanked before I hit 2 years and replacing the battery didn't help).