corrosion

I'm not an expert but I'd assume most reels would probably fare just fine in one day as long as you take the reel apart and rinse everything in freshwater right after you're done with it. Probably would be worth washing the line too. What reels are you using?

I just rinse my reels after each day's fishing. I use cheap reels, though, so I'm usually not too cautious. If you have any cheapos, it might be a good idea to use them.

I constantly use my reels in freshwater one day and salt the next.  I agree with Susquehannock.   Just rinse your reels (and all other tackle, including hooks and lures) in freshwater after use.  Don't be anal about it by spraying them too hard because it could force water inside the reel.  Keep your reels well lubed to keep moisture out (fresh or salt).  The important thing is to never let your reel become immersed in saltwater.  Then you probably have to take it apart and clean it.

All that said, saltwater plays havoc with everything metal and reduces lifespan.  Even stainless steel is not immune.

Just rinse off your gear it'll be fine, the worst is sand if it ends up in your spool. No reason to use anything in my opinion if you take care of it, I've done it for years.

If your rods are multiple pieces, be sure to not get sand in the ferrules.... penn battle 2 is my favorite inexpensive saltwater combo if you go that route

I have heard that you are supposed to rinse freshwater gear after use in salt. Over the years I have taken a variety of gear to Florida to visit the in-laws for a week or so. I just realized that I never did rinse any of it. Last trip was over a year ago and I haven't noticed any ill effects. I would say bring your favorite reels and rinse them if it makes you feel better (or if you drop them in the salt).