In reply to jimmccall:
Cotopaxi was a bit more active than I would like I was on it! We were warned of snowpack melting from underneath near the top. No idea what it's like now.
I forgot to answer the sleeping bag question of the OP. I sleep warm so use a 2 season for pretty much everything. When it's really cold, like at high camp, I wear all my layers bar the top one and a hat, and lay my down jacket over the top, inside the sleeping bag. This had always been fine for me and means I use all the kit I have, instead of carrying stuff up and not using it when sleeping. My tent, a NF westwind is also quite warm to sleep in. Only you can figure whether you're a warm or cold sleeper, admin helps too, making sure your hydrated with warm stuff as you go to bed so your sleeping bag warms up, make sure boots and gas stay warm and your roll mat is good (I use two foam ones.) And have a pee bottle so you don't lose heat going to the bathroom...