Depends if you are full timing or just a weekend camper or ??
For me, I'm only a long weekend camper during the summer months..
I don't venture far, so stick to pretty much the State Parks in Washington State.
In order to get my pick of sites, we can reserve up to 9 months ahead and I do that to the day.. I already have all my long weekend camping trips in the books since December 2018 from May to Sept 2019...
I got all my favorite parks and sites, so I just make the long weekends work.
But I work full time and this is the only time I can get away, so I need to know I have a place to go when I want to go.
It would be different if I were retired and just out there at any whim.. Seems like during the work days, Mon-Thur are them best times to be able to just drive up to a park and get whatever site you want.. It's the long weekend time (Fri-Sun) that are always booked up..
Good luck!
Mitch