That depends on the assembly line. The assembly the car line works like that: you get 45 seconds (or whatever time) to put your part one, then the car moves to the next station.
However I know of assembly lines where things spend several hours at each station. The people (often as many as 10 people per station) all work together for that time putting different parts on. If you can do the job faster than the time in station you can take an extra break to do what you want. Such lines are generally planned so that if you work as expected you get a 20 minute break when the lines move, most teams work faster and get a 30 minute break, almost never does some team get less than the 20 minute break planned.
The car model assembly line is the most efficient, but it has high costs. When you make a lot of something it is well worth those costs, but if you are only expecting to sell 100 "things" per year it isn't worth setting up the line.
However I know of assembly lines where things spend several hours at each station. The people (often as many as 10 people per station) all work together for that time putting different parts on. If you can do the job faster than the time in station you can take an extra break to do what you want. Such lines are generally planned so that if you work as expected you get a 20 minute break when the lines move, most teams work faster and get a 30 minute break, almost never does some team get less than the 20 minute break planned.
The car model assembly line is the most efficient, but it has high costs. When you make a lot of something it is well worth those costs, but if you are only expecting to sell 100 "things" per year it isn't worth setting up the line.