The overnights I've had were with girls I'd met for more than 1 30minute session. I knew that the overnight would go well as i'd got along with the girls during the previous meetings, had a lot of chat and a fair bit of craic with them. So I knew whatever we did I'd have things to talk about during the non-sexual moments.
We did various things at them - couple of times went for meals, couple of times went to a few bars for a drink and a dance, and then again also stayed in the room with room service, and sat out on the balcony casually drinking wine and chatting (it was a warm evening !).
I usually consider 3 sessions of sex to be quite reasonable for an overnight - once to start with, once before sleeping and then when you wake up before the overnight ends. Times have generally been 14 hours (7pm while 9am or 8pm while 10am) but have been longer once - met at 5pm and ended at 11am (having sex right up until we had to leave the room !) and then I spent rest of day with her, just having lunch and went shopping together...
AnthG - sure you will have a great time but remember - you can plan, but dont overplan, I would probably try and do what others have advised and perhaps have a slightly shorter booking with her first before to get to know her a bit more and to chat to her and maybe get a few ideas what she likes and then you can pick something that you know you both will enjoy and get the best out of your booking... thats the idea