Typically, if you’re pushing the 5-Year mark it’s time. Here’s the reason – the coating slowly starts to break-down and wash off, thinning the membrane as it goes. In time, you’ll see cracking, checking even peeling in the field or center areas of the roof that gets less water flow than the drains. You might even be able to see through the coating and see the black asphalt base. Remember this, the drains are where all of the action happens – where all the water is concentrated through a 3” opening called the “Scupper” and causes the most erosion over time. This is where 99% of all leaks occur. Over time between coatings, you’ll need to do the maintenance at the drains (patching, coating, etc.) to keep leaks from occurring. The drain is more or less a hole in the stationary wall of the house and the roof moves independently ever so slightly day in and day out. This causes the drain to crack over time because of the shifting and let’s water in your house.