I have these on a Mondeo, so not the most demanding car. I have checked pressures fairly regularly and never found them along way off the recommended values, but still within a couple of years have found them to be cracking really quite badly along the tire grooves, to the extent that the carcass is visible at the bottom of the cracks.
The tires are less than 3 years old, so age shouldn't really be a problem.
Having to replace these when they are less than half worn - so not best pleased. It looks as though I'm not alone if you check in the various motoring forums.

