Roof questions.Will a leak show inside before its too late?

then i guess next question would be, are pin holes common? i know every situation is different.. but outside of storing indoors all year long, how does one assure there are no holes anywhere? i go up twice per year with dicor and seal up the current seals.. that im ok with... its the rest of the roof that i worry about...kind of hard to detect holes on that big roof..arghhh. maybe i worry too much about nothing..haaha