You can waitlist whatever part you need or want. You stand a better chance having it filled the smaller it is. It is more likely one or a few days may open up than a full week or 10 days.
One thing to keep in mind that people sometimes seem to be confused about is that if the beginning of your stay is unavailable and must be wait listed you can not book subsequent days until the 7 month window opens for those days (ie if you want Nov 1-8 and Nov 1 is unavailable on April 1 you can waitlist the whole week but can't waitlist Nov 1 and book the rest of the week on April 1-you'd have to wait until April 2 to book Nov 2 if you couldn't get Nov 1 on April 1)