We recently did a survey to track the postmark dates on envelopes as they came in to our office. The results show that the bulk of the mail now arrives within 3-5 days of postmark. When holidays or holydays intervene, you can add two days to that average (5-7). While we still receive some mail within a day or two, some takes as long as 10-15 days.
If you have material which needs to reach us by a certain date, please give the letter a little extra time to make the journey. Also, realize that our response time is going to be a little slower.
It's not likely that mail service is going to get any better, so take the longer mailing times into account for all future mailings.