It seems like with these jobs that clean up, and maneuvering around merchandise and/or employees are two things that will eat up more of your time than you would believe.
You are right, doing these jobs at night is really the only way to do it. Otherwise, your fighting people the whole time. I did 5 gas stations where we replaced the T-12 that wrapped the exterior of the store during the day - this wasn't too bad since we were working on the outside of the store, but if we had of been working inside, it would've been a bear getting around all those people.