Yep, we face this challenge, too. We like to camp near Sarasota, FL in January every year to visit family.
Have tried several times to get into Oscar Scherer state park down there, but pretty much gave up. It is dang near impossible to get a site there in January. Have literally waited until the minute sites become available (11 months in advance). Literally, the split second they become available, they all book up before I can click 'reserve'. Its as if the system is rigged somehow.
We've had better luck with private parks, although they are more expensive. Typically, we stay at the KOA in Bradenton, its pretty nice.
That one, we only have to book it 6 months in advance instead of a year, hahaha.