It doesn't cost more to spend a couple of days with the girl. If the girl really likes you, then this is usually what she would rather do, because they mostly all want to find a BF. And even if they can't hook you into BF status, then it is still better for them to spend a few days with one guy, and have a steady paycheck, than to not know who they are going to sleep with that night or whether they will get a "date" at all the next night.
Of course, if they don't like you, then they will probably just want to skip out early, or charge you more if they stay for days, but why would you want to be with a girl who didn't like you for more than one night. :thumbsdow
So you pay the agreed LT rate, then they just stay with you if you invite them to. The only extra costs are for food and drinks. And, of course, if you take them shopping, there is extra costs for gifts!!
Remember this: They are mostly just sweet girls trying to make the best of it, and if you treat them nice and are fun to be with, then they will treat you nice in return, and they will be lots of fun, too! But you are not going to like every girl you meet, and every girl you meet is not going to like you. Use common sense and try to hook up with a girl who is keen to go with you, and don't waste your time chasing after stunners with an attitude!
JayBee