For an 8-hour booking with a 4pm ceremony, I'd start at 12:30pm.
The last 60-90 minutes of getting ready is what you actually want documented — hair finished, dress about to go on, mom helping with the back zipper. Anything before that is mostly "people sitting in a chair holding coffee." It photographs the same whether you're paying for it or not.
What I'd aim for: 12:30pm bride detail shots and final hair/makeup → 1:00pm dress on, last looks with bridesmaids → 2:00pm first look or solo portraits → 3:00pm guest arrival and ceremony prep → 4:00pm ceremony → 4:45pm family formals → 5:15pm cocktail hour candids → 6:00pm reception start. That puts you ending at 8:30pm with first dance, cake, and ~30 min of dance floor.
The trade-off: if you want exit shots (sparklers, getaway car, etc.), you either book a 9th hour or do a fake exit at 8:00pm. Most couples don't miss a real exit — but they regret skipping the candid dance-floor coverage.