"You can never be too safe." Yes, you can. How many of us bother to inspect the hydraulic brake lines in our cars before we start the engine and head off to work? Doing so would be safer than simply assuming that the lines were intact and driving off. After all, prior to launching a space vehicle, the people at NASA make no similar assumptions. They go through a countdown of all systems, taking nothing for granted. Erring on the side of over-caution is costly, and so is erring on the side of under-caution, though for a given choice, one might be costlier than the other.