We do ATH-ATL in our -300ers. It is blocked for 11:50 West bound and we need to cruise at about.80 to make it. It is about 5500 miles and we are limited on the freight but I have not seen any blocked seats yet. Maybe this winter.
There is talk about a few new routes that will require a horizontal rest facility this fall. Where they will be to has yet to be mentioned. We have a few -300ers from Gulf Air that I think have a little greater gross weight then ours (407K).