This morning I noticed circumferential sidewall cracking/crazing on all 4 of my tires. The defects are exclusively within 1-2" of the rim. They appear to be very superficial (I can't slide my fingernail into any of the cracks.) The tires are Michelin Primacy MXV4. They are 2 years old and have less than 5,000 miles. DOT stamping indicates they were manufactured 16th week of 2007. I keep them properly inflated. The car is parked outdoors but under a carport. It gets driven about once per week. How concerned should I be?

looks purely cosmetic to me ... I would keep an eye on it but, not be overly concerened at this point