I've had a few overnight stays with WG and SA girls, and the experiences vary from average to "OMG that was unbelievable". It's best to have a few sessions/dates before going into overnight arrangements, since you have to gauge chemistry and make sure you are compatible. A certain level of trust has to be built for it to be enjoyable for both of you.
With a mainland WG in HK, I booked an overnighter, she was HOT. It amounted to 3 sessions price (I think 4000 HKD), but I only got off two shots, one before she went asleep and another in the morning. I am not sure it was worth it.
With some of the SA arrangements, overnight arrangements have been GREAT. There is an added level of closeness which may be what you are looking for (or may not).
Know that you will have to tolerate each other's habits and sleep patterns, as issues like snoring  , passing gas,  , burping, vomiting / hangovers, etc all come into play. Like a real life SO or GF.  | |
, passing gas, 
, burping, vomiting / hangovers, etc all come into play. Like a real life SO or GF. 