How early is too early to start getting ready on the day of?

That's actually a little faster than what we're doing. Here's our (rough draft) timeline:

7:30 MUA arrives to set up

8:00-11:00 MUA works on me, MOH, and one bridesmaid

9:00 hair begins for me, MOH, one bridesmaid, and my mom

11:00 other two bridesmaids arrive with lunch for all

11:00-2:00 lunch/other two bridesmaids makeup (don't need hair)

My MUA suggested a longer timeframe. She said she can easily work faster, but on a wedding day there are so many interruptions. We are going to need to eat at least once. People might come in and out (doing it at my aunt and uncle's house), a dog needs to go out, someone needs to use the bathroom, someone forgot something, wedding venue calls, etc.

I was just in a wedding and we had 4 hours at a salon for hair and makeup for three of us. It took exactly the 4 hours. Bride forgot something and we had to make calls to get it delivered. We had brunch that everyone was munching on throughout the morning. We made mimosas. We chatted with other customers at the salon. The bride teared up and had to wait a few minutes to finish to makeup.

We are planning from 11 AM - 4 PM for our 5 PM ceremony. So 5-6 hours depending on what HAMU I choose. I have 9 bridesmaids, 3 moms, and me. I'll have 2-3 artists. I think 30 minutes per service per girl seems reasonable! I would just ask her how much time per person she needs. As long as the girls have food to eat and water to drink, and a place to sit, I don't think it'll be too long!

I actually googled this even though my wedding is over a year away. For late afternoon weddings people start getting ready in the later morning. I would trust her but I think she is on the right track regardless.