Well, 60-Secs insn't that bad. Just make sure you have three ingots on the bellow at all times, and turn it on when you see a customer coming to your door. Also make sure you have all of the grips and gaurds in stock. If you do all of that you should be find handling 1 minute orders. You could also have every type of weapon prepeared beforehand, but that's not really efficient until you get to titanium.
How far are you in the game as well? Im at admantine and I dion't get 140-second orders anymore.