Not really. The cracking of such material is caused by environmental factors such as sunlight - short-wave UV - and climate in general. Some people use ArmourAll (how ever you spell it) to protect tires, plastic, probably their head...but I've found that it actually hastens the process of having a tire fall apart. Another caveat is that if you get it on a rim, it has about the same effect as Teflon - your brakes will fail to stop you. So all you can really do is try to keep your tires out of the sun (yeah, right-just ride at night).

Pretty much you have to just accept the cracking as a consequence of getting older. Perhaps tires are like people in this way. Guess I'll go fill my bathtub with ArmourAll and have a soak....