I was able to do this 2x and was offered a 3rd time but did not partake.  Both times happened just by talking to them during a session and them saying they wanted to come along on a trip.  I paid for the expenses - one was a driving trip the other involved a flight and we didn't fly FC.  I paid for the meals and things like that but did not pay a rate nor was it ever brought up even though one of them had a weekend rate listed on their site that had a few 000's.

The first time we went out west a day or so before a conference I was attending.  We went hiking, caught a sporting event, layed out by the pool, ate great food, and had a lot of great sex before I had to put her back on the plane and I stayed for the conference much happier.  Felt so great that I ended up having great sex with one of the people attending who said I just oozed sex LOL

Second time the girl asked me if I just wanted to go on a trip - think she had some stuff going on here and wanted to get away and I just happened to be the person who had a session when she made that decision.  Driving trip and we had planned to do some activities before we went.  We never made any of those - multiple stops to have sex on the trip down - could barely drive and get to the hotel fast enough.  Had the best trip of my life and only had a couple of short naps the whole time.  Only time I ever had someone banging on the hotel door telling us to keep quiet - never had that with my ex for dang sure!  We had so much fun and laughed and had a great time for the entire short weekend.  Holy crap a great memory - wish she was still around.  Saw you even reviewed her years ago as well.

Just make sure you have a good connection beyond the sessions and it can be an amazing time so I would say go for it!

I have done trips multiple times under many circumstances. All have been pretty positive.
Like atlantajc most have been organic, just came about through discussion during sessions. I usually try to book lunch or dinner dates so there is more varied conversation than bedroom only dates.  
I do a conference @ the same time every year in Vegas and my client allows a very generous allowance for lodging – enough to cover a 2BR  Villa one block off the strip. For the last 5 years a top 50 TER lady I have been seeing for about 10 years goes along, shares the Villa and schedules her dates around by schedule when I won’t be there. She covers her transportation from her home city and insists on sharing costs of meals etc. We usually take in a show and over 5 days may play with each other 3 or 4 times – nice arrangement.
My best was my 70th. birthday gift to myself. 3 ladies from 3 different cities. Made all connections for them through ATL  so I could join them at that point on the same flight to St. Thomas. All 1st. class. Chartered a nice 42’ Cat w/3 bunks with a female captain and mate. Wasn’t outrageously priced since I was fortunately born ‘off-season’. We had an absolute blast for 5 days. No itinerary – just point and head that way. Ladies were 24, 32 & 41, all 9’s or better and all with great attitudes. One did end up hooking up with the mate but that was okay too. 2 of them discovered they really liked each other, and we did some doubles so that was fun too. The best week of my life and actually came in under budget.  
All 3 offered me the week for their 48 hr rate and one said she had so much fun that she offered me a ‘free night’ the next time I visited her city.  All are still friends and although they didn’t know each other before, 2 of them now tour together.
My other trips have all been great; but all with known providers and pre discussed extensively. You want to make sure every aspect is understood in advance.