Is my dryer outlet not getting enough voltage?
Have you inspected the dryer exhaust venting? These do get clogged with lint. I think I may have sometimes not kept our dryer vent as clear as I should have and maybe shortened the lifetime of the heater element in one dryer. 

My elderly neighbor asked me to figure out why his dryer was not working right. He had put a blower on the vent opening in the wall, but the results were unsatisfactory. Up on the roof I found out he had put a screen of hardware cloth inside the vent opening on the roof (to keep out animals) and it was almost completely plugged. Of course, I told him he could not have a fine screen there, and with his permission I removed it. I also had him use the blower from below while I pulled out caked-on lint from the top.

To test the wiring for voltage drop (including the dryer cord) you would slide out the dryer while leaving it connected, remove the cover on the connection block, and measure the voltages between the two hots and each hot to neutral. Then turn the dryer on high and remeasure the voltages. If there is excessive decrease in any of these voltages, that would indicate a problem in the house wiring or the cord.

To test just the receptacle and the house wiring, you would pull the plug out partway and use the voltmeter on the partially exposed blades of the plug without the dryer on and then with it on.