The buses run from 4 a.m. to midnight 'at regular intervals'. [=there is the same amount of time between buses]
It's nothing special, just a 'regular' [='basic'] stereo. = It's just a 'regular old' stereo.
He is one of the store's 'regular customers'. [=customers who shop at the store frequently]
(..) with your commitment to this meeting? And in that spirit, I'm gonna offer something sweeter. How about, once a week, on a night of your choosing, we go on a date. Just like a regular couple - dinner movie, ice skating. - Whatever you want. - Accepted. - You're very kind. (..)2015 Fifty Shades of Grey