The work footprint with only 4.5 hours per night of effective time will be pretty lengthy indeed. With Saturdays in November (before the ski season starts) being loss-making for most and seeing very little cargo operation, they'd almost be better closing from 0200z Saturday to 0600z Sunday for five or six weeks to let the contractors have a decent crack at it. The process to close and then safety assess to re-open a runway after works is not inconsiderable, and a 4.5 hour nightly closure is incredibly limiting, even before you factor any weather disruption into that programme of works.