Separate from the question on which o-ring to use, the issue of heat management on these multi stage hand pumps is critical. They simply have no good way to dissipate heat when pumped fast.
The stages are "nested" inside of each other, so the most heat is generated in the middle of the pump. That is why they need to only be used for about 50-60 strokes and then allowed to cool back down. This recommendation does not change when the pump is hooked up to a motor for automated pumping - the recommended duty cycle is for the pump and not the pumper.
Even if you do replace the o-rings with ones that will last longer when run continuously, you will end up having a hotter air charge leaving the pump, and this ill carry more water vapor into the gun or tanks that you are filling. That duty cycle of 50-60 strokes with time to cool down not only increases the life of the pump, but help to keep the air dry - it does this by keeping the air temperature cool enough after compression that water condenses out of the air charge to be vented out with the bleed valve.
Here is a post I made with illustrations of how the pump stages work. Note that the high heat third stage is buried deep in the pump - no good way to cool it: https://www.gatewaytoairguns.org/GTA/index.php?topic=145448.msg1477494#msg1477494