They won’t have a vote on each witness. Like in the House, they will have one vote on the structure of the trial and after that, the Republicans can do whatever the heck they want. McConnell will not allow a long, drawn-out trial.
Mitch already said that this would go for around two weeks (to include Saturdays). What could happen is that they try to subpoena Joe Biden and he goes to court to prevent himself from testifying. That would drag this out for four to six weeks.
Already backfiring on Commie Schumer, Collins is pissed at him.