I have a good customer who called me today, Complimented me on the work I was doing, and asked me to stop by in order for him to give me some money. He said that he is going out of town for a few months and wanted to pay the money up front. I am not complaining about this, just not sure how to appropriately handle it. Currently he is billed once a month on a 30/cut as needed basis. Should I estimate the number of cuts while he is gone or put together a per month charge for him.