I find the ambient temperature has no (or extremely little) affect on this unit, I have used it from 15 degrees to 100 with consistent cook times. This has been reported by many on here who live in extreme climates.
Another fiction I read occasionally, is by opening the door it will add 30 minutes to cook times. This unit is well insulated an recovers quickly. The bigger issue is bleeding heat off from cook temp to 140 when dropping to holding temp. I minimize any door openings but I'm not hesitant to open for removal of items with dissimilar cook times or other reasons. Recovery is very quick an I have not noticed a measurable difference in time.
Just my observations......