Man, I gotta say I see it the other way. Skipping the smoke test to save 20 minutes is exactly how you end up standing in someone's driveway watching the fire truck pull up. In my experience that test catches cracked heat exchangers and blocked flues that look totally fine from the outside, and a house fire is not a lesson you want to learn twice. Your mileage may vary, but I'd rather be late to the next call than explain to a homeowner why their place smells like burnt drywall.