You say the tires are 3 years old, does that mean that you installed them 3 years ago or you bought the 5vr 3 years ago? If you have had 2 blow on you then replace them all now no mater what, the rest of them, including the spare, are suspect and will go soon. Take it from me, no matter how old they are you still need to check your actuall weight on each axle and verify the air pressure daily when traveling.
Retired Navy Submariner
2014 Itasca Sunstar 35F; 5 Star tuned; 2014 Jeep Cherokee TrailHawk