DOT Number and Aged Tires:
All tires sold in the U.S. are required by the federal government to have a Department of Transportation number, also known as a DOT number, which contains essential information regarding your safety. This number is most often located on the axle side of your tire, meaning either you must crawl under your vehicle or put the vehicle on a lift to read it. ELABORATE.
Many U.S. and foreign tire companies are now warning consumers to discard of tires after five to six years from the date of manufacture; this is due to the rubber and other components within tires which break down over time, making older tires potentially dangerous, even if they look brand new. Although manufacturers do not give similar warnings in the United States, this is likely to change as lawmakers and watchdog groups, including trial lawyers, put additional pressure on tire companies to follow the same safety guidelines that are applied overseas.
Now to answer the question at hand, no you do not have to discard tires just because they are five years old. Have your service center monitor the condition at each PM service interval, or yourself visually each time you wash your motorhome. when sidewall cracks, lines, bumps, or anything out of the ordinary is observed, have a knowledgeable staff help you with your problem.