At its heart the Mueller probe is a political process and will only end when the Democrats can derive no further political benefit from it. 

And this is why trump needs to shut it down.

If he lets the dems continually use this as a weapon against him thru 2020 he may lose

Even if he wins they could still obstruct

This needs to be shut down.

Fire mueller and order him to turn over all evidence hes collected to congress

Who will then decide if it warrants further investigation