How long to wait after hatch day for Muscovy duck

My sweet female has been sitting... we reached hatch day 2 days ago and still no ducklings have emerged from the eggs... yet she continues to sit... how long do I wait until I can confidently say the eggs didn’t survive....

I would give her at least 5 days before I even tried to candle one. my Muscovy was really good at telling a bad egg and would kick out any she considered bad.

She’s at day 37.... and still sitting on all the eggs