The problem with impeachment talk is all of Trump’s crimes were things that were widely known (or easily anticipated) during the election. The voter’s saw these issues and still elected, it would be very hard to justify an impeachment based on them.
On the other hand, if the Dems can use subpoena power to find proof of Russian collusion or Trump deciding policy for personal financial gain that could change the calculus (although the Senate it still a huge obstacle).
Really I think the best strategy is to use the committees to start issuing subpeona’s and airing his dirty laundry. There’s enough scandals that they can plausibly drive the media cycle right up till 2020.