How far in advance should one shadow a dentist before applying to DS? I suppose it doesn't really matter, but I've read in several threads about asking the dentist for a letter of recommendation. I won't be applying until 2012, but I have some time on my hands and figured I'd like to get started with shadowing now. Assuming I finish most of my shadowing in the next few months, would it be strange to ask for a letter of recommendation two years before I even apply to DS?