My Escape has 2 different sets of Cooper Discoverer H/T tires on it. It has 2 on the rear that are about 4.5 years old and 40k+ miles on them. Still lots of tread (~8/32") left on them. The two on the front are about 2 years old and only 20k miles on them (they have always been on front tires and rotated side to side every 5k miles). The rear tires have developed some sidewall cracking (large sidewalls due to 225/75/15 size) about 1" off the wheel. Similar to the location shown here It is very small cracking like this other than where mine is cracked is only about 1/2" wide all the way around the outside of the tire. I'm not sure why this has developed. It might be due to the fact these two tires have been on the rear exclusively since the new tires were installed on the front. I think maybe there hasn't been enough weight on these tires to flex the sidewalls enough and keep the anti-cracking compounds in the rubber active. Other than that, I have no idea. It is kept in a garage at home when not at work. So back to the original question, are these urgent type issues or can I safely wait a year or so before getting new tires? Thanks.