Don’t forget that for EACH objection in the joint session of Congress on January 6 made by one congressman and one senator, Congress needs to debate (separately in the House and in the Senate) two hours over each objection. And then the two chambers need to reconvene the joint session.
And there are 51 slates of electors. And there are 538 actual electors. An objection can be made against each of the 51 slates. That’s 2 hours (plus additional administrative time to reconvene) times 51. Meaning well over a hundred hours of debating time and 51 times to regather.
Furthermore, (buckle your seatbelts) a congressman and senator can object INDIVIDUALLY against each of the 538 electors purported vote. That’s 538×2=1,076 hours of debate plus 538 times for the two houses of Congress to reconvene.
In short, one congressman and one senator can delay proceedings past January 20th.
Oh, and there’s a serious constitutional debate whether a non-member of the Executive Branch can become Acting President. The constitution says no even though the presidential succession act says yes. If the Attorney General rules the act is unconstitutional, then (is your seatbelts still buckled?) Secretary of State Mike Pompeo becomes Acting President in the absence of Congress confirming a winner of the presidential election (electoral college).
Alternatively, the Senate could have a contingency election for Vice President and elect Michael Pence. In which case he’ll become president in the absence of Congress declaring a winner of the electoral college. Because Republicans would also win a contingency election for president in the House, since Republicans control a majority of state delegations. So Pelosi would surely refuse to hold à contingency election in the House that Trump could win.