Unqualified to answer on the sub freezing temp and CF question but in general wouldn’t worry about a definitive lifespan on a CF frame. I would highly recommend, however, inspecting the fork steerer and crown. That is probably the highest likelihood failure point. Look for stuff that looks like your very unhappy seat post. I am not familiar with that brand but my 30 year old and 15 year old Colnago CF frames get regular use.
__________________
N = '96 Colnago C40, '04 Wilier Alpe D'Huez, '10 Colnago EPS, '85 Merckx Pro, '89 Merckx Century, '86 Tommasini Professional, '04 Teschner Aero FX Pro, '05 Alan Carbon Cross, '86 De Rosa Professional, '95 Gios Compact Pro, '95 Carrera Zeus, ‘81 Masi Gran Criterium, ‘81 Merckx Pro, ‘89 Cinelli Supercorsa, ‘83 Bianchi Specialissima, ‘VO Randonneur, Ritchey Breakaway Steel, Rivendell Rambouillet, Heron Randonneur, ‘92 Ciöcc Columbus EL