As a poll worker or a poll watcher? 12 hrs. is pretty standard for a poll worker. In my town the poll workers resent the poll watchers because they see the watchers working shorter shifts. They don't seem to understand that the workers get paid and the watchers are volunteers.
The only exception that I have ever known was 30 years ago in California when the used to hire a supplementary crew to come in at closing and help count the paper ballots. That often was an all night ordeal with all the Propositions. I used to do take that duty because I could leave the children with their father after work and join the counting crew at 7 PM. It was not unusual in a Presidential election to not get home until 4 or 5 in the morning -- and this was for a neighborhood precinct, just a few city blocks.
I have never seen a split crew in any other state where I have lived. This is why the poll workers are usually elderly folks. I've watched at some polls where the workers couldn't even count straight. I guess the reasoning is that with enough people counting and checking, the results will be accurate. But is sure seems like a dangerous way to run a country!
Been just a bit of Dem hanky-panky there recently--do you know what the Republicans are doing to stop it this time around?