In short my question is: Why does it usually take significantly longer than the specified timeout time to progress from one state to another in an engagement plan?
Detailed issue: A user has been added to an engagement flow and after the session has ended I can verify it in the EA supervisor and in the xDB. I have a simple engagement plan in which the first step has a timeout of 1 minute. I would expect that this timeout is more or less precise but I usually see that it takes somewhere between 10 and 20 minutes to actually progress to the next state. It eventually progresses which I have verified by using a simple action that sends be a basic mail, but it takes a very long time to do so.
Note: I am using Sitecore 8.1.3
(This question is a follow up question to Engagement Plans: Why is a user not added to an engagement plan until the session of a user is timed out? which is concerned with why users are not added to engagement plans until session ends)