Plumbing flashings are generally made of 2 different materials, lead or rubber.
Lead flashings usually will not give much trouble unless an animal has chewed on them.
Rubber boot flashings will last between 5-10 years depending on the weather. When you see cracks or splits in the rubber there is a leak.
Mid Cities Roofing can take care of these problems just give us a call at (817)656-2288