I was about to throw eggs away last time as nothing had happened but I candled them & thought I could see movement. I was then away for 24 hours (not great timing) and came home to both eggs hatched!
It's worth waiting I think. It seems to me that if they're going to hatch they'll hatch no matter what and if they aren't that's it.
Very exciting. Great to watch too. I'm hoping to actually be around for the next lot!