I have what I call a "Semi" seasonal site. A seasonal usually pays by the season/year, and electric may or may not be included in the price. If not included it's often metered and billed separately by the campground. Utilities usually remain connected for the entire season unless there is something in the agreement that specifies otherwise. The same applies to whether the RV can remain on the campsite or must be removed at the end of the season.
What I have is similar to what some campgrounds offer: You pay a storage fee to keep your RV in the campground's storage area. When you make your reservation, on your arrival day, the RV is moved from the storage area to a campsite. You'll pay a camping fee for the duration of your stay. On your departure day the RV is removed from the campsite and returned to the storage area. Most campgrounds move the RV between the storage area and the campsite for you and a fee may be charged for this service.
In my situation, I pay a monthly storage fee, but my RV remains on the campsite year 'round. I also pay a (reduced) nightly, FHU, site rental fee for each night I camp in my TT. When unoccupied, all my utilities must be disconnected and stored. However, I can leave my stabilizer jacks down since the TT will not moved.
Most of the previous posters have already presented their experiences, viewpoints and suggestions on seasonal camping, but here's one I don't think has been mentioned:
If you plan to remove your RV periodically from your site during the season for camping trips elsewhere, you might want to check the campground's policy regarding (what I call) sub-letting your campsite to transient campers while you're away.
