Just got my first piece of junk mail for an AU.
I added them in July, removed in Aug or Sept (don't remember if it was a one or two month one), got the first piece of junk mail now, in January.
The strange thing is it was addressed to them, but per the discussion above, I didn't think I got mail addressed to other people with my mail service. When I saw it addressed to a random name, I thought maybe it was a card, but nope, junk mail.
Just gonna shred all stuff addressed to AUs, cards or otherwise, was just curious about this one, if it was a card... turned out no. :)