I watched MCO-BUF for Dec 31st 2005 and the price never went down. I booked it as soon as the fare became available (middle fare group) and the price only ever went up.
Same story for BUF-TPA Dec 26 2005.
What dates are you looking for? You can also look on the Southwest web site, shortcut to fares section which shows you a month at a time. By looking at the monthly fare calendar, you can get a good idea as to what days would be considered peak and probably won't discount.