I've spent nearly 9 winters in Florida and while you can careen around without reservations, it's extremely frustrating. I know I tried that for 2 winters.
The closer you are to major cities the higher the rents. Ditto for closer to coastal areas or main attractions. Florida has tons to do where ever you go.
Make reservations now, maybe 1-2 weeks or a month at a time. There is NO rule of thumb how parks price and discount for longevity. It's all over the place!
Some parks are overstocked with pricey amenities while others have a lot less. While some parks will dip as low as $300 a month for rent, those are typically for annual rents. There are people who find a park they love so much, they just pay the annual rent and leave their rig year round, then visit it when the mood strikes them.
I've also noticed a trend in many snowbirders that are not off-season do-it-yourselfers (on maintenance etc.) tend to store their rigs in Florida year round then move them to their reserved parks when they arrive for winter.
Because snowbirders tend to be an older crowd, every year folks die or get too ill to travel, so the parks have winter vacancies to fill at odd times. So it's worth checking back every few weeks to see if anything has opened up in future reservations.
Last summer I bought an RV lot yet I had prepaid for an upcoming winter in another park. I knew my friends had a crummy spot reserved, so I called them up to take my nicer reserved spot. We then did a conference call to the RV park to see about cancelling my reservation but transferring my friends to the lot, so I was able to get a refund and they were able to nail down the spot with their funds. The park still stuck me with a $20 processing fee, but my friends were thrilled to get a great spot before it was snatched up by someone else.
Florida is a year round destination but Jan-Feb-Mar are definitely packed with snowbirds and those without reservations are moving around every few days and sometimes boondocking which can be very difficult to find in Florida. I spent some spring and fall time careening around so I could see more areas and enjoy more parks on a trial basis in case I wanted to return for longer stays in the winter.
I have visited many RV parks I wasn't staying out so I could see what they had to offer and if I wanted to stay there in the future. Typically I asked if I could park and walk around, only one place in 8 years said no. The others I took my doggy on a walk around the park, so I could get a closer look and feel for the place. Hey, if the dog didn't like it, I didn't either. :
Some parks will let you do a drive around to look-see others don't want the extra traffic, hence me asking if I could walk around rather than drive.
Good luck. Think outside the box and you will find reservations available.