Does anyone have any real world experience with how many actuations can be expected from a 40D? I believe Canon says about 100,000. If so, should I have no problem with buying a used 40D with around 40,000 actuations? With my XSi, I've put about 16,000 on in 18 months. So, I figure I would have about 5 and half years worth of camera if I remain at a similar pace. Am I thinking soundly or should I be more concerned? Thanks in advance.