I don't candle eggs until they go to the hatcher either. Now if I needed the space in the incubators I might but since I am incubator rich I just don't bother messing with them. I figure the more you handle the eggs the longer they are out of ideal conditions and the more likely they could get exposed to some infection. Now if I had a a 20 egg incubator and I was holding eggs for a week or 10 days at a time I would probably check the first batch so I could add more if some weren't fertile. Depending on the color of the egg and how much intensity you have to candle with I don't know if I would trust the 10 day candling anyway.
BTW my DH spent nearly $100 after paying shipping for a brinsea candler. It had great reviews. I am not at all impressed. My little high intensity flashlight works a lot better. What a disappointment. I begged him for it for Christmas so I just haven't told him it isn't what it is cracked up to be. The best thing I have found to date is a flashlight called the Pelican StealthLite 2400. It has a real high intensity bulb and you can see very well into eggs. I guess I should have been satisfied with what I had.
BTW my DH spent nearly $100 after paying shipping for a brinsea candler. It had great reviews. I am not at all impressed. My little high intensity flashlight works a lot better. What a disappointment. I begged him for it for Christmas so I just haven't told him it isn't what it is cracked up to be. The best thing I have found to date is a flashlight called the Pelican StealthLite 2400. It has a real high intensity bulb and you can see very well into eggs. I guess I should have been satisfied with what I had.

My clock/therm on the egg tray was reading 97, so I turned up the dial and after an hour or so, it read 98. So I turned it up just a teeny tiny bit more. (I'm now waiting to see what it's going to read) I'm pretty much right back to the factory setting it came with. Figures!!!!! I guess I'm going to ignore that glass reading entirely. Thanks for the harbor freight suggestion-- we have one of those, that would be easy to run down and get one. However, I just bought that fancy-schmancy digital RH/temp and it should be here today or tomorrow. I'll stick with my travel clock/therm for now. I didn't realize how under prepared I was. I am kicking myself for not buying that a few days earlier. I thought i had time. Poor eggies. I hope they make it.