Can A Listing Agent Realy Only Work M-F ?

We all know how many hours we need to put into this business to be successful right? I thought we did, but seeing wording like this on MLS from listings agents makes me wonder. "Seller ( this is a nice way of saying listing agent right?) kindly requests that all offers be presented to the xyz listing agent via email, fax or hand delivery, between 8am-5:00pm, Monday-Friday". So the question is... Will this work? Will no weekends really work in the real estate business? Please let me know if we are just crazy working 6+ days a week???