In reply to Simon Preuss: I just spent two weeks in my Asolos Llotse GVs, no other shoes with me and did a fair amount of miles on snow free paths - not a problem at all for me. Had one blister on the back of my heel but I had that before I left, due to new work boots ads it didn't get any worse.
The La Sportivas all had a slightly roomier heel it felt to me but everyone's feet are different.
I was dreading the whole hols in B3 boots but as it happened... no probs.