A lot of people here seem to be thinking it doesn't make sense for Satoshi to just stop posting, leaving emails unpurged etc.
I hope this throws some light on that.
Some facts about terminating a throw away identity:
On the crypto lists back in the 90's we already knew that Carnivore was recording email contents at ISP's under gag orders, Enigma was operating, and data recorded at choke points into and out of major land masses. You also knew there were copies everywhere, in backups, in other peoples email accounts as well as their backups, etc.
From the day you created an alias like this, you would be ensuring there was nothing linking it to your real ID, and if you screwed up it was already too late to fix.
Exit from the alias then didn't require a 'last login' to purge email, and in fact that might have been more dangerous (if you were terminating it because you suspected surveillance)
Satoshi might not have been around then, but we're sure he read that stuff carefully since that was when the building blocks for bitcoin were created, and the early attempts at digital cash were tried.
His security mind set may not have been created then but was surely influenced by those discussions.
So, no need to be thinking he was careless or must have died to leave things as he did.
It was the exit plan all along.
That's it, but many people don't understand his cleverness.