Here are my expectations (which are not a prescribed etiquette)
Email:
1) for most relationships—one day
2) for intense relationships and efforts to organize meetings—several times per day
3) for work—as many times a day as needed. I only check email a couple of times a day, but it should be a lot more often.
Text messaging:
1) for initial message—one hour for a response—after that, a day for acknowledgement
2) at indeterminate end—an hour
3) at clearly defined end—one day to forever
Chat
1) live chat—as long as it takes to type, and the little sign should say you are typing
2) semi-chat—a few minutes up to fifteen minutes. After that I assume it’s over.
Phone
1) professional—that day (hah! my contractors can take a good deal longer than that)
2) personal—maybe a day—two is stretching it
Paper correspondence
1) does anyone do this any more?