Not sure exactly what pink slip you're asking about because there are a few different types of pink slips.
Pink Slips for drivers ed do not expire.
The pink slips for vehicles never expire either.
The title, or pink slip, does not expire.
You never have to pay a fee once you have a valid title.
For drivers ed the pink slip is proof that you participated in and completed a drivers ed course.
It shows that you are on your way to becoming a responsible and safe driver.
You must bring it with you to the DMV when you apply for a provisional license.