The number of videos available varies, yes.
If you do too much farming, then the supply of videos for you may dry up completely for a day or two...
If you need to use greens to get the condition of your players back up to maximum, consider using the free video for each player via the training menu. I use this all the time (you have to make sure you can complete it before your match). I don't need to farm and the supply of videos stays at a high level.