There was a thread in this section a couple of months ago about this topic. If this link doesn't bring you to it, it was called "How long do you give management" and it was in the Audit section.
Previous Thread 2 weeks was the norm. I said shorter, but I have since changed to 2 weeks also. I agree with Sid about no suprises and that the long times allow them to "forget" to respond.
Welcome aboard! I was in your shoes last year. If you register with BOL, you can PM me and I'll be happy to help you out. Or, you can always post here. Everyone has been very helpful. Either way, good luck! It's a lot of work, but worth it when you get everything running like you want it.