How long is too long before the wedding to be ready?

As far as your hair and makeup holding properly, 5 hours should not really matter if you've picked a HMUA that you trust and that understands your skin/hair type! I would just be prepared to do touch ups, which isn't uncommon in general.

That is a really long time in between.
Our ceremony also started at 5:30. I had my hair done at 12:30 and makeup at 2pm. I wanted my makeup to last so had it done the latest possible. We did first look at 4pm followed by family pictures. I didn’t do getting ready pics and only had a Best Woman and Best Man.
We were done with pics by 5pm. I was ready by 3:15 and waited until 4:00 which felt like a long time.

You could stand to move back hair & makeup, but don’t move it back to much so there’s cushion time in case the artists run late. I’d say consult with your photographer on a safe timeline plan.
We had a 3 PM ceremony and wanted a First Look, so our photographers recommended that be at 12 PM. I told my artists the last woman, MOH, needed to be done by 12 PM (I figured it’s fine if she’s still in makeup close to 12 since the First Look is only me and FH). My artists ended up running us late though (kind of stressful I’ll admit 😬) Our First Look didn’t happen until maybe 12:30ish - 12:45ish. We actually ended up still finishing First Look, Wedding Party, Bridesmaids, Groomsmen, Groom & BM, and me & MOH on time for the transportation to the church though! I was impressed and my photographers said “Oh we baked the cushion time into First Look and Wedding Party photos in case of the artists running late.”
As far as the getting ready photos, all we got was the tail end: hair being finished on me, dress & veil being put on, and him putting on cuff links, tie, and jacket. We did miss getting me and the women in the matching robes & PJs, but I’m surprisingly not remorseful about that (believe me, I thought I would).