“I think that when the lies are all told and forgot the truth will be there yet. It dont move about from place to place and it dont change from time to time. You cant corrupt it any more than you can salt salt.” - Cormac McCarthy
Recommend not leaving home without it... or atleast a plan for 20+ extra degrees of protection.
i prefere the bag /[pad route as well..i carry good poly pro's for extra warmth in the fall and winter..plus i have diffrent bags set to the temps i expect...i have a very small merlin patrol bag for summer( good to around 40)..a med bag ( good to 20)..and a winter bag(-20)..i add other clothing layers to just be sure.....often when i lay down on cool nights i put my bag at my feet..when i cool down i will pull the bag up as aquilt...if i wake up cold i get inthe bag and zip up..
on the other hand in summer i usually wear a pair of running shorts and sleep on the pad( mostly for skeeter protection)..my lite bag is at my feet incase i need it...
The issue is how to stay warm with sub-issues of comfort and convenience. There are as many sleep systems as there are topography, climates and weather system differences and whatever system chosen must match up with the typical conditions of the area. But safety on the trail is always paramount. How far away from help -- both in distance and time -- impacts on how much and what gear to take on the trail. The harder it is to bail out quickly the more the backpacker will have to plan for extremes and the sleep system should reflect this. But there are always lines to draw...you can't carry all gear for all events. That requires that the backpacker know the terrain and trail conditions, know the weather forecast, and know his/her gear before hitting the trail.
I know it's apostasy here, but if conditions get critical and your sleep system is not sufficient, you can always boost the range 10 degrees or so by dropping to the ground.
Last October, I embarked on my first hammock hanging backpacking trip. Temps dropped from low 50s to mid 30s w/ 15-20 mph steady wind with no warning from the weather forecast. I was cold even with a pad, wool sweater, fleece bag & fleece hat.
I learned to be prepared 15-20 degrees colder than the forecast. even for a short trip in the mountains.
Take care & be careful