Just to save you some work... you NEVER have to call daily in this situation. For a 10 day reservation, just call ONCE on any of the third through sixth days after you made the original 7 day reservation. You are GUARANTEED to get the extra days.
(Lets say you called on January 1 and reserved seven nights, December 1-8. Nobody can stake a claim for that room until you check out - starting a new reservation on January 8 with the 11-month window. As long as you call back once between January 4-7, you cannot lose that extension.)
For us veterans, day-by-day calling was necessary at one time. It changed when they switched the 11-month window based on check-in day instead of checkout day. BTW - walking only works for the 11-month window reservations.