If applied right, you will NOT have to re-do if for many years. The commercial roof coating in use is rated for 10 years. The Hospital where I work the original rubber roofs carry a 15 year warranty and are going on 20 years old now with only the occasional leak due to puncture damage from someone being careless while working on the roof. Remember a commercial building owner wants to forget about the building for many years and demands performance. I would expect at least 10 plus years from the liquid rubber coating if applied correctly.
GSMC(SW) U.S. Navy (RETIRED) 1967-10-03 to 1993-11-01
1995 Gulf Stream Scenic Cruiser, Cummins B5.9, Allison MD3060, Toad: 2005 Focus ZXW SES Wagon