For a straightforward roller swap - door already off the opener, tracks straight, no spring involved - the work at the house itself usually runs under an hour once the tech has assessed which rollers need replacing. Add a bent track that needs adjusting, or a second roller that looked fine until the door was moving and turned out to be seized, and that time stretches.
What we won't give you here is a same-day promise tied to Mount Prospect specifically. The crew works out of Skokie and the ten miles out means a call gets slotted into the day's route, not treated as a walk-up. That's not a knock on the town - it's just how a single-shop operation covering this much ground has to schedule, and we'd rather say that plainly than imply a response time we can't back.