Tires: dual tire equalization, dual tires, dual tire

Question
How important is it to have exact pressure in each of dual tires? Are the devices that keep equal pressure really helpful or is a 1 - 1.5 lb pressure difference ok? Does this pressure difference change under use as the advertising says?
Thanks much

Answer
M,

Yes, the pressure differential between duals is important.  Pressure buildup is differnt between them.   1 to 1 1/2 psi is OK, but Zero would be better.

But I think the biggest advantage to these pressure equalization devices is that it makes checking the inside dual so much easier.