Schedules are an important part of being staff. Real life is a priority over minecraft though.
In my opinion, I do not think this would increase/decrease your chances of being accepted. We don't accept staff because of their schedules. Staff members are accepted on terms of maturity, skill, and knowledge. Although being online over summer is a great help, I do not think it'd increase your chances of being accepted.
I may be wrong though. Yuko and Purple are in charge of applications. Another staff member will correct me if I'm wrong.
Have a nice day!