In reply to testagrigia:
> It takes 45 days to acclimatise fully to 4,000m.
That may be theoretically true, but not for practical purposes. Most people can do a 4,000m peak without ill effects after a week or so and feel fully acclimatised to 4000m after a fortnight.
45 days is what it takes to climb an 8000m peak, not an Alpine 4000er!