In terms of threat and error management, hand flying an aircraft for long periods in busy airspace increases the potential for making errors
In these discussions re automation and manual flying skills, I don't recall anyone ever advocating "hand flying an aircraft for long periods in busy airspace."
Credit must be given for a common sense approach to hand flying practice on line. Unfortunately it becomes a vicious circle where, regardless of company rules, there are captains so apprehensive of switching off the automatic pilot or flight director even if conditions are fine, that they refuse to allow their co-pilot permission to keep their hand in.