Airlines are keenly aware that timeshare folks usually go from Sat to Sat. You can use a service like Kayak to monitor the rates for you and notify you of the changes in costs. I think most of us check regularly and sometimes get lucky with a temporary drop in price. That does not prevent the possibility of unexpected changes like a forced overnight or additional stops to be added by the airline before your trip but then you may have the possibility for negotiating some changes that work better for you.