If they are the original tires? or I were going to tow it down the road I would take off (1) tire at a time and replace all. You cant tell by (Looking) at these tires,the age. Take the (1) tire to the tire shop and they can tell by the # what age the tire is. Ps read past Posts on tires,you can take a tire off quicker than reading All the Tire post.
Youroo!!