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]
(..) -Charlie. -On your way somewhere else? -Passing through. Looking around. -Funny to see you. -Funny, isn't it? You boys are a regular family business. You boys are a little late. -What did you find? -I found some interesting prospects. Did you hear Standard bought up? -Mostly in the north, so far. (..)2007 There Will Be Blood