Matt, it isn't necessary as long as something doesn't lodge itself into your float valve!
- relying on the float valve to hold back all the fuel is bad practice...but likely your 'friend' hasn't been unlucky enough to experience what you just did!
To make this task easier, I added a 2nd fuel shutoff petcock in the engine compartment where I can reach it...as Caleb mentioned, the way I remember is to hang the key on it..I still have the original petcock on the fuel tank itself, but it is a pain to get to (under the galley, steps, drawers in the way, etc..) so adding another one at the main Racor fuel filter is much more convenient and gets used regularly. If the float valve fails, only the fuel in the line & carb would leak..a much easier cleanup.