I know this may vary by person so really there's nothing scientific about it... We're off to WDW for 10 nights in Sept... 2 adults only so I booked studios for the stay. We're at BLT for 5 nights... I originally had a standard room but I changed it to a lake view at my husband's request. We were very lucky to get a boardwalk view studio at BWV for the last 5 days after being on a waitlist for only a couple of days....
Now I am contemplating wait listing for a 1BR, 4 of the 5 nights are (or were) available the last time I checked so there's no guarantee we'll get the waitlist....