Looking for ideas

I have an office with 21 Associate Brokers that have the opportunity to stand floor time in order to get costomers when they call in on floor calls.  I have been a Realtor for just over ten years and have never seen floor duty or floor time to work very well and it always seems like there must be a GREAT way to do floor that is fair and productive.  We currently have two floor times each day, one from 9am - 12:30 and the second one of the day is from 12:30 to 4pm.  Then the phones are forwarded to the afternoon floor person at 5:00pm and any and all calls through the evening.  The phones are un-forwarded at 8:30am.    Any ideas on how to do floor duty that would be more productive?