I believe, that's too global a statement. The taller you are, the more injury prone you become. It's mere physics. Just look how long certain guards have lasted in the NBA: Mark Jackson, John Stockton, Steve Nash ....
If you are a penterate and pitch/score guard like Iverson, Westbrook, Lin etc., you will have less time, but if you generally keep you feet on the ground, take longe range shots and pass first, you have a better chance to stay in the league for a longer time than a heavy big man with considerable playing time.