Re: Professors: To have the best prospect of making a sale (for *both* the Fall OR Spring courses) you should land your offer exactly in late March: later than that and decisions have been made. Alternatively early February. If you have to mail in the Fall, the best time is September. What you are trying to avoid is the months when profs come back from vac to mountains of mail and discard things en masse, or when they are cleaning up their desks in preparation of vac (or research). At other times a good flier can still land a course adoption, but it is slightly more of an uphill battle.