What causes cracks in tires

[Apache]

My tires start cracking way before the tread is even half worn. I have had to replace tires prematurely a couple of times.
I check the air pressure every time I ride and even change the pressure when MRS. A rides.
I run Harley tires (Dunlop I think). The scoot is kept in a metal building with plywood floors.
All I put on the tires is soapy water and nothing else.
Anyone got any help?

[Guns]

Age is usually the main cause of cracking, but somehow I doubt that is the problem you have mate.
Extremes of temperature can cause it as can exposure to direct sunlight, but that usually takes some time to happen.
Exposure to chemicals could be another but I get the feeling that none of these apply to your tires mate.
Not sure but I will certainly ask around

[Apache]

It does get about 10-15 degrees hotter in the building since it is just a metal storage buliding.
I just hate to see the tire go bad that soon.
Dunlop told me not to put any preservative or UV repelant on the tire, they said it was already in the rubber composition.
Thanks