Dont think the harsher weather thing is true, if they have a good coat on them, they will do fine in any weather
no matter if living in doors or out, my lot all live indoors and can stand any weather.
From army experience mate, a week in the field and you forget about the cold. A life time would make you immune to it. Also like when lamping out the window, you feel a chill, get in and put the heaters on, you feel good, then get back out the window you feel it 10 fold.