One of the things that keeps our community from using discourse more for day to day interaction is that it is not as immediate as email. In the ebb and flow of a workday it is jarring and odd to members that messages take so long to be delivered. So we still use cc lists in email or a google group for timely messages.
We value the ninja edit window and have it set to 10 mins for posts in discussions:
We would greatly value having another setting like this for messages to allow them to have a lower ninja edit window or none at all. Or the ability to have messages sent out immediately as are password reminder messages.