I have 2 "Big Buddy" heaters. They can use 1 or 2 of the disposable propane tanks. My oldest heater was primarily with a bulk tank, hose, and a special filter designed especially for the Big Buddy. The filter screwed in where the disposable cannister would go and a standard hose connected it to a bulk tank. I frequently had a pressure issue if I turned on a full 20 lb to quickly. So, when the newer stoves came out with a dedicated hose for attachment to a tank, I bought the newer one. I have used my big buddies to heat a 120 sq ft dome tent in the fall in Wyoming with no difficulty. Temps went below freezing at night but not much below. I used it for heating up the tent for a sponge bath before bed time and when getting up in the morning. I did not sleep with it on because I didn't need to. I have also used it for the same purpose in a Jumping Jack trailer both here in Colorado and in Wyoming.
I also have it for use in the home in the event of power failure and I have used it in the bathroom of my mtn cabin to get things toasty before showing. I have used it above 8,000'. I haven't used it in really serious or severe weather, say single digit temps but I wouldn't hesitate to run it all night in either the tent or the tent trailer. I do however, make sure I have a bit a vent to fresh air available.
When the trip is long and the temps are expected to be cold, I use the newer heater & dedicated hose with a bulk tank. If it is a summer trip or a short trip then I use disposable propane cannisters. Two will last me 4 or 5 nights (+) for just warming up the tents before bedtime and in the morning.
Hope this helped,
Steve