I saw a house in early November with a Christmas tree in it and thought it a bit soon. It doesn't bother me, I think it's fun, but for me I'd say around early December...
I can understand shops doing it early as people budget for Christmas in the last months of the year, they don't do it all in December. But I tend to ignore the Christmas displays till November...
I don't like to judge in all honesty, but just thought it an interesting topic!
You never know someone's situation - I vaguely know someone who had a son in the army and his closest leave to Christmas was in October, so his mother put up decorations to have Christmas when he was at home... sadly he never came home and she now still puts her decorations up at that same time every year