somewhat regular use keeps the tires flexible and rearranges the 'sitting' forces that focus on small parts of the tire that create stress and cracks..
keeping the sun off the tires stops the uv exposure as well as lowering the temperature which softens and promotes cracks..
tire covers are cheap and easy way if parked outside.. they can be found online or most rv parts stores..
not a fan of tire dressings, can't stand the sticky brown gunk that builds up.. I use
westley's bleche wite to clean tires and leave them naturally clean..
I'll let y'all google your own preferred dressing brands, but some are reported to be more detrimental to your tires due to the chemicals..
or just plan and budget tire replacements as a fixed expense like oil changes, belt and hose replacements, etc..
good luck y'all!