I'm fond of cutting it off.

For an ordinary panel, you can cut it off, and for a talking scene, you can cut it off

When you want to show the expanse of the space of a background, you can cut it off

To each his own!

There are people who don't like to cut panels off at all (gag manga/non-fiction manga), and there are people who cut off every panel (battle manga) Do it the way that you like and suits your style!