I have had my 70-200 for almost two years now and it has performed flawlessly up until now. I have shot about 50 weddings with it and no issues. Now it it having problems focusing at 200mm. 70-185 it is very sharp but at 200 it almost looks like slight motion blur or just plain out of focus. I can get it to focus accurately sometimes but most of the time it is just off. I am sending it in to Canon but do lenses get out of calibration like that? It has never been dropped or mistreated. On another note how often should you just send your lens it to get it checked over and professionally cleaned? Especially if it is used a lot.