There is never a guarantee that any Skysaver seats will be available on any specific flight at any time. It depends on the load factors mentioned above as well as other factors about which nobody is really certain in terms of the factors or how and when they are applied. Most FTers agree that Skysaver seats have been reduced in number recently as the FF mile promotions have made it easier to get the miles. In other words, you can get more miles but you'll have less opportunity to use them. Not exactly a consumer-friendly trend.