Cars parked on concrete in a garage over nite are driven the next day or so. Keeps the polymers mixed in the rubber.
Trailers sitting on concrete or any surface for weeks/months at a time before they roll again can flat spot and may dry rot inside. And they look fine.
Carlisle and Goodyear are our oldest trailer tire makers and have storing recommendations.
Goodyear;
http://www.goodyearrvtires.com/tire-storage.aspx Carlisle;
https://www.carlislebrandtires.com/news/tips-for-storing-trailer-tires Tireman9 rvtiresafety blog says this about tires on rv just sitting;
**Rubber strength degrades with time and heat with HEAT being an over-riding contributor. Do you cover your tires with white covers? This can result is a very significant lowering of tire temperature. Every hour of full sun exposure can be equivalent to two to 3 hours of use running down the highway at top speed.
Quick example: 8 hours a day 7 days a week for two months each summer can be the equivalent of 10,000 miles use as far as rubber degradation is concerned. So if we assume a tire is good for 40,000 miles and you park it as in the above example after 3 years you may have "consumed the equivalent of 30.000 mile tire life, just while parked.**
All tire mfg have storing tires recommendations. Check yours out.