Not at all. That wouldn’t be much fun for anyone! Just like other types of dairy farm with other kinds of milking parlours, the frequency of the milking varies from farm to farm.
It is typical for cows to be milked around twice a day, but this will also depend on the size of the parlour and whether robotic technology is installed or not.
If there is a robotic system in place, then the cows can decide when they would like to be milked, and they can choose to let themselves in and out of the parlour at their own leisure.