Time is how long is the cleaner in contact with the soil and the surface. Too short and the soil won’t be removed. Too long and you are wasting energy and have excess downtime and run the risk of redepositing. There is also a component of time to consider with respect to time between use and start of cleaning and time between cleaning steps. In the brewery, it is almost always easier (requires less time, action, cleaner, temperature, etc) to remove fresh wet deposits where there hasn’t been a chance for excess microbiological growth to occur than it it to remove the same deposit later. It all falls under time considerations.