I am well beyond that mileage with no side wall cracking or belt separation etc. My 2104S is parked outside year round but the tires are covered when parked.
If you are going to worry about it obsessively go ahead & get new ones, they will be well worth it. If you check them before every trip, then you have some more time but I wouldn't go over 6 years from the date on your tires. There are several discussions here about 'china bombs' with blow outs in their experience. It reminds us all to be careful including the tires on our TV.
2013 Rockwood Mini Lite 2109S
2010 Toyota Tundra 4WD