Walking at 7 months can sometimes work if your only competition is other members who are also booking at 7 months.
As an example, let's say you want to book 11/18 - 11/25. You start watching the RAT a week or so ahead of 4/18 to see what resorts will be possible, knowing that 2 or 3 nanoseconds after the window opens, the week you want will be gone. You notice that 11/16 &11/17 are still open - that's the Friday & Saturday nights before your desired vacation is set to begin. On 4/16, you book 11/16 - 11/23. (If you got the last room available for that week, you have now shut out anyone else who wants to book the same thing you want. On 4/17, you call MS and drop 11/16 and add 11/24. On 4/17, you call MS and drop 11/17 and add 11/24. You now have the week you want.
Could an owner block you by booking part of what you want? Yes, of course, but most owners will already have booked (they don't usually wait until the last minute) and even renters who are interested in "your week" will probably already have booked. They pretty much know to book early in the 11 month window to get what they want and they are willing to pay for that assurance. The odds are in your favor.
So in some cases, walking at 7 months will benefit you. IMO, the number of those cases is rare, though.