Not sure where you are at on your journey, if this is an urgent thing or just looking down the road. Any extension needs to be pre-approved, especially if scholarship is going to cover it. My guess is there has to be a good reason. I am not sure particulars for Navy, for Army a 104R document that shows the entire plan towards graduation is listed, my daughter did plan on summer school classes her first toe summers just to keep her class load down, and we paid for those. When she transferred majors one of the stipulations was she could not extend past the original graduation/commission date. Asking your chain of command the sooner the better and make sure you have your “why” ready to explain. Good luck and keep us posted.