When buying off of boards, I allow 2-3 days for the parts to ship out and a week for delivery typically before I start harassing the seller. Honestly, I seem to find slower response from some of the "dealers' than I do with Joe Shmo. I have actually had some impressively quick shipping from individuals recently. I paid one guy in Cali about mid afternoon here in the Midwest and literally had a tracking number from him about two hours later. He printed out the shipping label online and ran it up to the post office as soon as I paid him. Got the part in like two days! Couldn't beleive it.
I try my best to ship everything the same or next day. Stuff does come up though. This winter has been rough as well between all the flipping snow/ice and flooding. I have to admit though, I also tend to be less motivated to ship out a $10 envelope by itself and will wait to try and consolidate a few things. Maybe some of the people are waiting until the end of the week to get a few things to ship at a time.