There are some good answers with good advice. I can think of a few things to add to what the other answers have said.
You did not mention if booking the studio includes booking an engineer or technician who will be running the studio equipment or if you are bringing your own engineer and simply renting the studio time/equipment. I am going to assume that there will be someone connected with the studio who will act as an engineer and/or producer.
If this is the case, you should solicit their advice after clearly articulating your goals and the willingness and capabilities of your band mates. Ask about how much time in the studio makes sense. The engineer/producer will know from experience how much time will be spent getting set up to record the entire band at once. They will probably have some insight based on experience as to how many takes will be needed to get the desired end result.
He/she will also know their own post production capabilities with regards to post production mixing, tweaking, editing, "splicing" and mastering. Depending on the way you set everything up (a click track is important) the engineer/producer may be able to take the best parts from several different takes and seamlessly blend them together so that playing a song over and over and over trying to get the perfect take may not be needed. But only the engineer/producer you will be working with will know if that is a viable option given the equipment used, skill of the producer/engineer, and the set up.
Another thing that will be important is for everyone in the band to get plenty of sleep the night before each session and be sure they are well hydrated before going in. Regular breaks should be included in the session. You might want to decide you will take a break between songs instead of a set time. You don't want to interrupt the creative karma once you get rolling, just because it's time for a scheduled break.
If everyone gets tired and starts getting sloppy, it might be time to stop playing and spend the balance of the booked time planning for what you hope to accomplish the next day and/or talking about what you are working on that day, or listening to the various takes. In fact when I have been in the studio, the first half of the time is spent performing and recording the various takes and at least as much time is spent listening back to decide which parts of which takes I like best. If this is the approach your producer will take, then by the time your band mates start to get tired of playing, it will be time to do some listening to what you have played.
There may also be some listening between takes so you can talk about what you like and didn't like about that take. So if you are in the studio for 8 hours, it's likely that you may only actually be performing and recording for half that time, with the rest of the time spent listening.
Finally, be sure the band members are committed to treating the booked period of several days like a serious job. Since they have to go to work the next day, they should refrain from staying out late partying after the work day is done.
Good luck and have fun.