Cold weather idling 2018 Cascadia DD15

I run Alaska trips through canada and bought an 18 cascadia with dd15 (save that opinion lol) because i needed some better mpg. That being said in 10 to -45 degree temps the truck stays running 24 hrs and when sleeping 8 hours I find the 600rpm idle the motor cools down and oil pressure is very good and the dpf filter doesnt fill up and no dpf regens but if i high idle the filter gets full and regens and obviously uses a lot more fuel. If I am able to stay warm at low idle with my webasto heater and keep good oil pressure 40 or 50 psi (the main reason i idled up was to increase oil pressure in other trucks) without plugging up filter and regen why wouldnt i want to idle at 600 and save the fuel (fuel very expensive up north $8-9 gal usd)?