Basically the relation with a dome is a human interaction. I am not comfortable at all with tipping, it seems to cheapen it. Again all the mistresses I meet are independent and usually they charge at least $300 an hour. Once I get to know and like a mistress while I don't tip I might gift her, the same I would a good friend, and it is never something from a wish list.
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Never try to teach a pig to sing. It wastes your time and it annoys the pig.