cigarette's time
The time it takes to smoke a cigarette. One cigarette's time is the time it takes to smoke one cigarette. Two cigarette's time is the time it takes to smoke two cigarettes and so on.
Person 1: How long will it take until you get here?
Person 2: It shouldn't be longer than two cigarette's time.
Person 2: It shouldn't be longer than two cigarette's time.