You can close batches whenever you wish and it is very easy to do so!
You will want to hover over near the batch name on the left menu, and click the icon with three horizontal lines. This drops down to show you 3 icons. One is a Pencil (for editing the batch name), one is a Printer (for printing all labels), and the other is an X to close the batch.
Once you have confirmed you have closed the batch, you can always view it again by going to List>Closed Batches. Here you can restore your batch to open, review data, export or even print labels if you ever needed one.