Hi
I am only on my 3rd hatch (but first natural hatch). My broody hen is sitting on duck eggs, I have candled all the way through, usually after a few days to check all were fertile, and then periodically to check theyre growing... and they are... phew! Mine are due to hatch on Monday.
But I do think it depends on your broody. I reared mine from a chick, in an incubator, she knows me as mother hen and seems to trust me, never gets upset when I approach or remove the eggs. so knows Ill give them back. So promptly tucks them under with her beak, which I love watching!
In fact I currently have two broodys sitting, the other is sitting on duck and chicken eggs. Again, I have candled (mainly because I find it fascinating!) but also to check they're not dead.
With my first broody now due her first ever hatch on Monday I wont move or touch the eggs. Up to today I have lifted her for 10 mins a day for a poo and a stretch. But I wont now as it's important that those eggs have consistant heat and I dont want to lose any humidity she is producing.
I posted some candling pics a couple of weeks back. I'll see if I can find the link.