I don't have issues with it being a sweep job but folks best be bothering me about it because I don't read your letters and even when I do I'm certainly not going to decide when they're finished for you. :P

But yeah, locking them in place seems like the best solution. Archiving them seems like it would introduce a whole different dynamic and I'm not really keen on that plus if there was such a thing as 'dead letters' I would rage about it.