In reply to stratandrew:
Hi Andy,
I've been twice in July and climbed two of the mountains that you mention, with long stays at 5300m. We had -20 degrees c at dawn but it felt warmer than that if you know what I mean. I have always used double boots in the Blanca because I like to put the inners inside my sleeping bag to dry them out properly over night, and I haven't suffered with cold feet. Double boots give you a bit of insurance in case anything goes wrong. If I was going this summer I'd take Scarpa Omegas and sell them over there at the end of the trip
On the last trip my partner wore his LS Nepals with an insulated super gaiter, I think that they were Berghaus, and he was fine with that. On an earlier trip a different partner wore Lowe single boots and he got really cold feet with frost nip. It stopped him summiting on Chopicalqui.
If you're doing any tech climbing take a big trowel sized adze for the flutings
have a good trip........Jeff