To change the keyframe default settings
         
         
            - Select Edit > Preferences and
               open the 3D Tracking page.
            
 
            - Enter
               the keyframe Step value. A step of
               approximately 15-20 keyframes is generally a good trade-off between
               computation speed and accuracy. 
            
 
            - Enter the Maximum keyframes.
               This value allows you to limit the calculation time regardless of
               the sequence size. 
            
 
         
         See 
                     Keyframes.