When you perform a lot, getting ready tends to break into a kind of science, depending on how much time is involved.
If pressed for time, I can do it all in half an hour: make-up, hair, and ready-to-go in costuming. And be solid and ready.
Ideally, I like to take about 15-25 minutes for make-up/hair, and have a good 10-15 minutes to futz around with my costuming, and 10-15 minutes for a nom/brain collection time.
And when I really can, give me two hours so I can linger in a bath (after teaching a day of workshops especially), take my time eating/snacking/de-braining, and the rest getting ready.
(and if I have to change costumes between sets, I can do it in under 7 minutes, though prefer 10-15 minutes to adjust if necessary, 20-25 minutes if major hair/make-up changes are involved)
So there you have it: as a professional, I can do it all in half an hour, but I'll gladly take about 2 hours if I have the accommodations and means to do so. Most often when I am performing, I have taught for anywhere from 2-8 hours that same day, and if it's at a big event, probably took a workshop as well. And if I traveled far to get there, I'm probably doing it on less than 6 hours of sleep. Also, if I am traveling with the band, I'm going to dancing for at least 35-45 minutes, versus a regular bellydance show set that may be 6-7 minutes, or 12-15 total. For the record, I am NOT superhuman or abnormal - I have seen many old school pro's do the same in the same time or less, and they're 10-20 years older than me.
Hence my deep confusion and utter bogglement when folks tell me they can't take a workshop that ends 4 hours or more before showtime (or AT ALL that same day), because they need to prepare for their performance that night.
Sure, performing is important. Doing the best job you can, especially. But it's not the end-all, be-all of the dance experience, and not THE most important thing. For me, it's about the learning and sharing that happens in the classroom - what happens in class has much more longevity than any performance. And time and time again, I have observed that those whose butts were in the workshops with me earlier that day, versus the ones who "needed the day" are consistently more successful on stage. Same with teachers who told me they prefer to perform vs teaching - that they feel teaching is the only way they can get opportunities to perform - yet, their performances haven't grown, nor have their teaching technique over the years.
Also, I believe there's something to be said about actively pushing both your brain and your body the same day you're going to be performing. On days when I only perform (not teaching or taking a class earlier that day), I always feel as soon as I get off stage that NOW I'm ready. It's not enough to run through my set several times before I go on - I need to expand my brain and body past that piece to fully tap into what's possible. It helps shut down the left side of the brain, and really engages the right brain. And whether I have taken or taught a class that same day, it's ALWAYS given me something else to consider for my performance that evening. Much better than any amount of make-up.
True, there are extenuating circumstances for some folks, who have really valid reasons - family, work, illness, etc - but I think that most often, others have bought into this idea of the "sacredness" of performing - that they must save themselves all day for those precious 4-9 minutes on stage. But if one actively works in the performance arts (music, dance, theater, etc) - this simply doesn't exist. Rather it's full-immersion, full of practices, rehearsals, workshops, and other preparation - every day, that make for a successful performance.
I think it boils down to, if we want to be truly professional in our dance and outstanding in our performances, it's going to come from working both your body and brain beforehand. Then you can make it pretty.