A Henyey track is a track along a H-R diagram (HRD) showing the evolution of a pre-main-sequence star (PMS), i.e., each point on the track indicates the position of that body at some point in its life. Time on the Henyey track can be considered an additional PMS phase after that on the Hayashi track. It occurs with stars more massive than red dwarfs, i.e., those that do not remain fully convective, instead forming a radiation zone. Such stars continue to collapse and the Henyey track ends when the collapse ceases and hydrogen burning begins (though these may not be simultaneous), i.e., the star enters the main-sequence and its movement on the HRD is much slower. On the Henyey track, the star's luminosity changes less than on the Hayashi track, i.e., less up/down movement on the HRD. I find little information about the amount of time spent on the Henyey track: the original paper included timescales in millions and tens of millions of years but considered this to be rough at best. Another source suggests less than a million years.