When I book a session into my studio, I want a minimum of 2.5 days per song if the songs are of average length and complexity. This is based on drum tracks being recorded at a rate of 4 songs per day; with a full day for editing, overdubs and vocals; a full day for mixing; and a little extra time as a contingency for each song. Of course booking more time takes the pressure off everyone and usually makes for a better outcome.
Pro Tip 1: Get ready for the vocalist to be sick right before he is set to sing.
Be prepared for tuning problems to eat up overdub time in tracking rhythm guitars. Hopefully you will have enough time in the studio to write a new ending to a song if you need to, create hook melody parts to underline the choruses and tighten up lyrics in the verses. And hopefully you will have time to really have fun in the studio without the clock burning a hole in the back of your head. Even for just a few hours of glorious creativity.
Pro Tip 2: Get ready for the band that says "we are totally prepared" to not be prepared at all.
On the other hand, if you have too much time you might think the song needs children's choir, pan-flute, orchestral bells or chanting monks. Or worse yet, too much time and you may never finish the album. I know this sounds counter-intuitive, but it's quite true. I always suggest putting an absolute ending date on the recording. Embrace the results, and don't second guess unimportant details.