How much ice is a jockey box going to use, if my event is all day long?

Our 54 quart coolers will hold approximately 35 pounds of ice. If your jockey box or jumper box was set up properly to begin with, In a 3-4 hour event you may, or may not have to add ice. There are several factors that will contribute to ice melt, non of them having to do with the actual cooler itself.

How cold is your keg to begin with?
How much beer, or other beverage, am I pushing through the jockey box?
How long is the event?
How hot is it outside?
Am I keeping the keg cold?

Most of the time, we do not have to add ice. But have back up ice just in case, or if you will be at an event for an extended length of time. So ~35 pounds to initially fill it, and have ~35 pounds on hand, for backup.