You have made the need for reservations lower by not travelling much in the summer. The exception is the snowbird areas, especially southern Florida, from late fall through the end of February. Prime state parks and national parks down south also need reservations year round on weekends and holidays.
I tend to plan and reserve ahead of time because that is just the way I am. That helps me avoid dicey parks. I always consult RV Park Reviews and rarely get led astray. Planning is not stressful for me, but scrambling for a place to spend the night or staying in a park with poor facilities and management is.