How Long Can A Hen Leave Her Eggs, And Still Have Them Hatch?

Depend on how long she has been sitting if only a few days then the 5 to 6 hours it wont hatch... But if its a a week or so already she can be off the whole day and the eggs will still be viable.  My hen sat in the wrong nest for the  whole day I found her the next day day place her back and within a week most of the eggs hatched...

Some birds will not leave the eggs at all and rely on the cock to feed her some will pop out to get some exercise or to get food for themselves or have a quick bath its dwn to the brred of bird how they act and the experiance of the pair on wether they leave the eggs to long for example a hen that migh not usualy leave the eggs att all might b forced to leave to feed if the male is not doing his job. Theres many variables the best you can do is not disturb at all and ensure the nest box is of a correct size and thickness to give the birds adequate room but good insulation so the nest stays warm whilst ensuring it wont be to hot for the young once they hatch as your birds get older and lay larger clutches of eggs you may want to increase the size of your nestbox

She can be off of them for at least five minutes if they are still warm...if she has been laying on them for a week to three weeks then there is already a baby inside the egg so if she refuses to lay on them any longer you are going to have to find a way to keep them warm without the mothers help.

I had one clocker come off her eggs one day.  I was lucky it was in the summer and that I had another clocker down.  It was at least 5 hours be for I knew.  I put them under the other clocker and luckily I had 2 hatch from the 6.

They can leave them for 10 minutes or a bit longer in the warmer months and they leave the nest the day before the eggs are due to hatch (learned that one the hard way) I thought she had abandoned them as they were cold to touch. We put them in an incubator anyway and now they are hatching but won't be accepted by the mama hen as she is off consorting with the neighbourhood rooster again!

If you can please help,
I don't know if the eggs are still alive p.s how do you tell ?.
And we have a broody Chicken in with the other chickens but all the others are still laying and she is siting on them one not the fertalized one's we brought. (as we don't have a cockral) . I think she was laying on the normal eggs till about 3.00 when I looked. So I got them normall eggs from underneath her and placed the fertalized one there and we normaly let them out about 7.00 so it was 9 hours she was off them. And they were cold :/
please please please help :)

I have personally had a hen that abandoned her clutch that she had been faithfully sitting on for two weeks.  They were left for three days unwarmed.  I was at the trash can about to toss them and opened one up to find a LIVE chick inside.  I quickly put the rest in an incubator and had two out of 8 eggs hatch.  They are more resilliant than you think!

During a rain storm, a collection of water dropped down on nest of eggs, hen immediately went and sat on them again, will eggs be OK? They are about 15 days along.