I've a marmot never-summer bag. I also carry a -8 degree silk liner in case it is too cold for it. I love it.. super warm.
In Colorado when we ride/camp in the mountains (often between 10K & 13K feet) we can get below freezing every night of the year.. so I have that bag with me every overnight ride and if it is warm I just sleep on top of it.
The best part about the bag? It is KTM orange
One of the keys for cold camping is to use a 4 season tent... much better protection from the elements.
I have a half dozen tents that I use on the bike.. I choose the one that is best for the particular ride I'm going on - but the sleeping bag stays the same.