So, is this something that my HVAC co. could adjust? Or is it hardwired and buried?

Just as a followup after many months on this. We recently had the fan motor on our condenser unit die. I originally thought that the defrost board had quit working, so I spent a while looking at it.

I learned that- 1)Rheem/Ruud has demand defrost control (guess they originated it) and 2) there is a jumper on the defrost board to set the coil temperature that defrost terminates at. The default setting is 70F, with options for 80F, 60F, and 50F also. Ours is now set at 50F, which won't affect how often defrost starts, but I'm hoping it will reduce the duration of defrost (and cost) without impacting HP performance. I've never seen frost on the outdoor coil.

I'm a technical guy, but I admit to fumbling to figure things out that I don't look at very often. I did actually come out ahead on this- my HVAC service company wanted $600 to replace the fan. The motor was $100 and it took me maybe 1/2 an hour to trade out.

With demand defrost and heavy snow or any type of precipitation below freezing the unit will probably defrost a lot more than when its 30 and dry outside and it rarely goes into defrost mode. The demand defrost option will still pay for itself in comparison to a timed system.

I'm not arguing against demand defrost. Mostly I'm just glad to have figured out that there is a little bit of adjustment to the controls. I'm used to setting heaters in (unmanned) industrial facilities to maintain at 45F. I don't see a need for my HP defrost to run up to 70F every time it runs (which seems like every cycle when it's moist and in the 40's).

We'll see if it has any effect on cost to operate (always hard to tell a change anyway).