I have an extreme dislike for standing in queues and waiting. The worst is standing in the airbridge, while people settle in. So whenever I fly with an assigned seat on the plane, I try to board as late as possible. I rather wander a bit on the airport then queue for some time. I don't mind the lack of storage space for cabin luggage, since I usually travel light. 

That is why I try to postpone boarding as long as possible, but still I manage to end up standing in the airbridge most of the time, even when I thought I was pushing the limit.

Is there a rule of the thumb to estimate the latest time to board?

== Edit ==

No I don't want to be the person everybody is looking at because he delayed departure.