I personally only candle once during incubation - on day 18, when I'm preparing the incubator for lockdown, and when it's so easy to tell which eggs are good and which are not. However up until last year, I'd candle at least one egg every day. It's so interesting, and quickly becomes a habit. It never effected my hatch rates, though.
In fact, last year I did an 'experiment', where I marked an egg, candled it, took pictures/video and wrote down it's progress every single night, from day 1, up until day 18, and he was probably the healthiest most determined chick out of 18 others! I'd try to narrow it down to candling once a day, rather than 2-3 + times a day. That being said as long as your light isn't getting too hot on them, and as long as you're being gentle, and not allowing them to cool down too much, I don't think it'll hurt. Good luck.