How long is too long to incubate eggs?

[chookpalace]

Hi all
This is my first time using an incubator and I have borrowed one to try it out. As far as I can tell I'm using it properly, with constant temperature checking and water in the bottom, turning eggs x3 each day etc. It's not the fanciest incubator, in fact it's one of the cheapish hexagonal ones but has been up to the job previously. I have had some issues keeping the temp absolutely constant but have managed to keep it between 97.7-100.5F all the time except for once, about a week in when we had a power cut for 2.5 hours and they dropped to about 86 degrees at the lowest point (but not for the whole time- I tried to wrap them up etc). Anyhow, had candled before and after this and definite signs of life both times. BUT today is day 22 since I put them in and no sign of hatching. How long do you think I should leave them before I give up? Is there anything I can do to tell if they're still alive? Do you think I'm likely to get some chicks in this scenario?
Any advice from more experience people would be appreciated!

 

[yinepu]

I always give chicken eggs til day 24.. then if I have some that have not hatched I do a float test

 

[Gypsy07]

If your humidity has been okay, I'd think you could still hope to see some chicks in the next day or so. Everything else sounds like it's been fine and the short drop in temp might just be slowing them down a little bit.