303 Protectant every other month when in use, and a good spray coating before putting rig up for any length of time.
Going on almost 8 years with our 3 slide Lexington. Original seals and wipers are still good as new.
Seals are rubber and will deteriorate if not treated to keep plyable. They'll dry out just like any rubber product.
My slides stay in when rig is not in use unless I'm out playing with the rig.
Also, much much cheaper to buy it by the gallon...$37.00 now on Amazon with free shipping. Get a 3 buck spray bottle and your set. A gallon will last you a looooong time as a little goes a long way. Still working on a gallon I bought 2 years ago, and I use it on our motor home, 2 Subarus, and a pick up truck, on all the rubber and vinyl on the vehicles.
Steve & Cheryl + Zoey, and Ziggy, our furry kids.
2012 Forrest River Lexington 283ts
Toad, 2013 Subaru XV Crosstrek