If it was started now it would be in full swing during the 2018 midterm elections.
From the Clinton impeachment, which I lived through, we know that the public does not like it. The feeling at the time was that impeachment thwarts the will and the vote of the people. 62 million voted for him and an attempt by the losing side to remove him will not set well with those 62 million and also those who are not died in the wool democrats. In other words the 20% in the middle will likely vote against those dems who try to impeach him. The dems in office know this and will only pay lip service to their base to try to quell their anger over their loss in the election.
While it might be therapeutic for the dem base to talk about impeachment, it isn't going to happen. Trump supporters should just let them alone to vent their frustration. After all, it could have gone the other way and we would now be talking about impeaching HRC.