Misconceptions about allnighters:
All night sex; wake her up whenever you want: It does not mean all night sex. Most have a minimum # of uninterrupted hours of sleep time. Most do not include a morning romp in this service. Ask yourself what you are expecting, cuz you are not going to get that.
First time meetings: It is not always available on a first visit; many sps require at least one 1-2 hour appt before committing to all night, or at least a long conversation.
A favour or a "good deal": No, you are not doing them a favour by providing dinner or other meals, booking a longer time, hanging out.
Should be much cheaper because of the longer time: Social rates are cheaper than the hourly fs rate, but they still charge for the additional hours. Look at it this way, time spent with you is time they are not booking full fs hours with other clients. 4 hours on dinner dates is much less than 3 fs hour appts, which she could have booked if she wasn't committed to this 4 hour dinner date. (That is an extreme example, but in general while in an extended appt she is not able to schedule up to 2 other appts, nor is she able to take calls and make appts for other times while on the date).
Oh, I was going to add: if you post something in adult gigs or casual encounters on CL, I can guarantee that the only women who reply are going to be sps lol. Even the CL ad "never done this" is a pro looking to sucker you in, and even she is expecting 500 for only a few hours not overnight.
You just need to lower your demands, get your expectations into the real world. I guarantee you can have a great time for that 500 with an extended date, but frankly you are taking a lot of risk if you demand or expect a good encounter for 500 on an overnighter.