Well, I discovered a few days ago what the issue is, now I just have to pinpoint the location of the problem. By listening to the furnace every time it came on, I discovered that on occasion it will not spark. Within 10 seconds of turning on, there is that distinctive "click" most times, but if it doesn't do it, I know it didn't fire.
Hoping to try and clean up and troubleshoot accessible connections this weekend, but at least for now, I know to cycle it right away, instead of having cold air blowing in for a few minutes before noticing.
1992 Dutchmen 30FK
2 adults who don't know they are adults, 3 furry feline children