Let me tell you a little story to prove a point.
A clever man travelled the world with a jar making money from a particular bet that he made with those he came across. The man would fill his jar up with rocks and ask onlookers put their money in for double the return when they thought his jar was full. When the rocks piled to the top of the jar, most of the crowd would place their bets and think themselves a winner whilst others would look on in curiosity. To their disappointment the man would pull out some smaller stones, place them on top and give it a little shake till they fell in between the others. A few others make their bets then only to watch the man tip a handful of sand into the jar and still manage to fit more in. By now there seems to be no more free room in the jar and the lucky few left think they have it in the bag. But surprisingly, the man picks up his drinking water and tips the last few mouthfuls into the supposedly full jar. By now the man has become much the richer and he continues on to the next unsuspecting crowd.
If tl;dr, the point is there will always be a vulnerable window of opportunity in any security context. The idea is how small is small enough for your requirements.