At my previous job, the most productive time was when I was serving my notice after resignation, I got 6 months worth of work done in two. Without all the status updating meetings, "quick questions", overtime due to incidents, and whatnot, I got a lot done.

It was a bit ironic though, as most of the work I did during that time was ultimately shelved, as I can tell by looking up public DNS entries, probably due to other people exiting or the team being reorganized.