Looks like there'll be some changes to AskTom coming sometime.
"I'm rewriting the site :) will be locking threads after 4 weeks (will allow for emergency bug fixes to the content to be alerted to me of course - so they won't be locked totally, you'll still be able to comment on them but if the comment isn't relevant to the existing text - a question about how it worked or pointing out a mistake - it'll never see the light of day)"
I think it will be an improvement. At the moment there is the conundrum of not wanting to miss anything, but also not wanting to plough through text from the several years ago. Plus topic drift makes searching more difficult as you can get lots of results returned where the titles don't seem to match what you are looking for but you need to look at the article to be certain.
The trick for Tom will be managing late comments that are 'sort-of' relevant. Maybe some will make it as distinct questions in their own right. To avoid that becoming a route for bypassing the "I'm not accepting questions now", you could simply hold off posting those as new questions for a week or two so that people get the message that it isn't a 'fast track' for answers.