To plan a school year field study during the summer months takes about 30 minutes whereas to find the phone time and plan the trip once the school year starts takes about five hours. That's why I make those field study calls during the summer.
The only problem with summer planning is that it's difficult to let others know about these dates--others who also schedule meetings and other events for you. I suppose it's important to send them an email even if some do not like getting emails during the summer months. Better that than problematic planning in the days ahead. Onward.