Please look at post 2498 on page 250
https://www.backyardchickens.com/t/835798/5th-annual-byc-new-years-day-2014-hatch-a-long/2490
It's about the importance of turning early in the cycle.
If you're sure your air cells are intact, the longest I'd wait to turn the turner on is 1 or 2 days.