"Why not just saving the content of the etherpad in the dedicated wiki page at the end of the day?" <- Yes, that's what we do. Sorry, if I wasn't clear. I am agreeing that we can have an established URL for the bug day etherpad.
I'll explain what the process has been for the past two bug days. The etherpads I have created for the past two bug days are based on the months they were held, e.g. http://etherpad.wmflabs.org/pad/p/BugTriage-2013-01 and http://etherpad.wmflabs.org/pad/p/BugTriage-2013-02. I was following Bug Management's Meeting Preparations page. Before the bug day, Andre links all the bug reports from the query we are working from. The first bug day had ~170 reports and I can't find the number of initial reports for the second bug day. During the bug day we comment below each link about actions we took or questions we have about that report. The information we archive on the bug day pages are the reports that have comments under them, which we assume are the only 'addressed' reports, e.g First Bug Day's Page and Git/Gerrit Bug Day's Page.
I agree that we could have one Bug Day etherpad, since we save the reports we address on the event's bug day page.