The bees are quick to notice when the honeycomb cells are empty – we guess empty cells must feel quite different underfoot if you are a bee.
We have found the bees will sense the cells are empty and straight away begin uncapping, repairing the wax in the cells, and refilling.
You can watch them work on uncapping the end cells as soon as you reset the Flow Frame to the closed position.
Usually they finish uncapping all the cells in a day or two. If the hive is not so busy (the colony is on the smaller size, population-wise) it may take longer.
In our experience, a slower hive can take up to a week to uncap all the cells on the frame.