Let's say You have a loyal slave that You've owned for a few years who lives near You and does various things for You along with making routine tributes of say $100 a week; let's also suppose that one of the slave's most rewarding tasks - which You realize it looks forward to and takes great pride in - is to wash Your car once a week.
What would you do if another sub, who contacted You and was in Your area, had a particular interest in washing a dom's car, and was prepared to pay You $150 each week for that privilege but was otherwise not interested in any other form of service. Would You take the task from the committed slave already serving You and give to the new slave? How would You handle a situation like this?
(Note: this is totally a hypothetical question asked to get a sense of whether most masters operate the same way or approach situations differently - and perhaps to spark an interesting conversation; this bears no relation to any personal experience or issue in its own arrangement with its master.)