the right pressure for a pressure tank

I recently had a new pump installed and my system serviced. I replaced my Square D 40/60 switch because my contacts were shot. A "friend" recomended that I adjust the switch to a 50/70 setting and only put 40 psi in the pressure tank. I heard that the 50/70 setting is better for the pump especially when you have an irrigation system, which I do, but I never heard of setting the pressure 10 psi below the cut on pressure. Could you help me understand this concept or is my "friend" just looking for a return visit to replace the pressure tank?

Pressure tanks should be set two psi below the cut-on pressure.
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Mike

Like Mike said, 2 psi below the on pressure of the pressure switch.

The most important thing is to not cycle the pump while sprinkling. Set the pressure so the pump keeps running throughout the entire zone. If the 70 psi isn't able to do the job, add more heads or increase the nozzle sizes of the heads.

bob...