Check your roof at least once a year if you are physically able. Otherwise, get someone else to help with it. Your roof bakes in the sun all year long, so there is a lot of expansion and contraction. It is also subject to high winds, hail, and tree branches. Finding out there is an issue with it when a long period of rainy weather hits is a disaster. I had a kitchen ceiling ruined once because I was overly confident that my steeply-pitched roof would never leak, especially when the shingles looked fine from the ground.