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]
(..) -Hey, George. -Hey, I'm starving. Last one. Listen, you gotta help me out. Elaine and Puddy broke up. He's treating me like a regular customer. I tried to tell you, but you wouldn't listen. No. You were gonna get a deal. There's no law in this place. Anything goes. It's Thunderdome. (..)1998 TvShow: Seinfeld Title: The Dealership Season: 9 Episode 11