You cannot assume that you will show up in the Fall and have a spot on the roster. As other have said , you need to show up in the best shape of your life, prepared to battle for a roster spot and battle for playing time. Many D3's will have 50-75 players in the Fall, with just 35 roster spots available.
Yep - son's first day at practice had 53 players show up (D2 JuCo). They eventually self cut to 35 (grades, medical-health, disillusionment) by the spring season.