Nancy Pelosi can sit on the Articles of Impeachment all she wants. In fact she can sit on them until the 2020 election is over.
But of course by then President Trump will have won his landslide re-election. The Senate Republicans majority will be increased. And the Republicans will have retaken the House, and Nancy Pelosi will no longer be the Speaker.
The new Republican Speaker can continue with the program set by the Democratic Party and hold on to the Articles of Impeachment. This action will of course anger and cause the symptoms of Trump Derangement Syndrome to worsen in Leftist neverTrumpers everywhere.
Now in 2022, the Speaker of the House after the mid-term elections of that year can send the 3 year old Articles of Impeachment to the Senate, if the 2022 Speaker is a Democrat. If the Republicans still have the majority in 2022 then they can continue to hold on to it as the Democrats did in 2019.
But finally after the 2024 elections. The new Speaker of the House, no matter what party, can finally send the 2019 Articles of Impeachment to the Senate. Of course by this time the Senate will dismiss the charges since President Trump will have completed his 2nd term and will no longer be the active President. And a vote or trial wont matter.