I do it whenever it feels like my brain needs a reboot, that is, when my mental processes seem to be frozen and don't flow properly. That's like a pair of times every day. Some days more, some other less.

Nothing fancy, I just sit there breathing and take everything else out of my mind.

Since I do it when I feel I need it doesn't feel like a waste of time or anything like that. I know I'll be more focused after meditating and will do a better job.