How long can an (muscovy) egg be unattended and still be viable?

[RebinNH]

So my muscovy has 1 egg that for about 5 - 6 days she is broody on but so far has left it each day for a few hours. It gets cold. Is it worth this? I assume it may be not be viable, as I went in there and a couple times it was cold.

 

[DemeterAD9]

Odd that a duck would brood a single egg but not impossible. Ducks will take breaks when they are broody so it's normal. The length of time they are off the nest varies and a young hen may stay off longer. If you want to check development grab a flash light and sit in a pitch black room, at 5ish days you should be able to some veins.