For us, I have tried a few different ways of handling this request. Starting out, I would give discounts, offer free days, and include extra tonnage to contractors, thinking that would make them loyal to me. In hindsight, I only lost money! Price yourself fairly and kill the service end. Your model has to work for you. If you only have a few dumpsters, you can't afford to have them tied down for long at one site. I would only add dumpsters when the calls are outnumbering your count. Slow and steady will keep you from going under. I would offer exchanges every other day instead of dropping two. That way, you will keep his job moving and have something available for the next customer when they call. It will also give you the ability to run loaded as much as possible, increasing your exposure when the dumpster is on your truck for new customers to see you. Unloaded or loaded, these things seem to get the same fuel mileage, so keep the billboard rolling. Most contractors are not used to this level of service from a dumpster company. Loyalty comes with consistency.