That shouldn't effect you being cast, and if it's an issue for casting and they are interested in possibly casting you they will usually ask you during the audition if you can take a different day off or just not take it off all together. I was going to ask for a few random days off but decided to go with full availability and if I need a day off I have points to use, but that's something I hope to avoid doing.
I guess I'm special then because it took me longer than the other internals I know to hear back, hah hah! But the general rule is if you're internal you don't hear back as quickly as someone who's non-internal but that doesn't always mean you're waiting forever, and this year they've been quick with casting emails. There's still people who auditioned about a month ago who are still waiting on emails.