Since in most cases you will be paying for your studio time, you want to utilize it in the most efficient way possible - but the key words there is MOST EFFICIENT. A huge mistake that is often made in the studio is not knowing when to take a break or call quits for the day altogether.
It's common to want to keep going and get as much music recorded as possible no matter how tired and worn out you or your band is getting. But if you force yourself to keep recording when you are exhausted then the only thing you might be doing is recording it now, just to have to go back and record it again.
Not only does your body, vocals and the ability to hit notes start to suffer, but your ears and the way you hear things suffer too. Your ears won't translate the same sound the same way to the brain when you are exhausted opposed to when you are refreshed and feeling good.
That's right, pushing yourself when exhausted can result in the performance as a whole suffering, and after a good nights rest, you might listen to it the next day and be very displeased with what you hear. Like with every part of our body, our ears get tired, and no matter how long you keep playing they won't repair back to normal until they have had some rest.
It's just like sports and the reason why coaches have a second and third spring of athletes to switch in and out. When the main players get tired they are unable to play at an optimal level until they had some time to relax and rejuvenate. You need to treat your ears, vocals, fingers, arms and the rest of your body the same way, you need time to rejuvenate if you want to hear something spectacular on playback.
It may suck taking a break or quitting until the next day, but what is the point of recording if you are just going to have to record it again. Sure, technology these days can mask a lot of mistakes, miscues and half-hearted playing, but nothing beats a performance that is killer from the get go.