You probably could go through a lifetime and never have a flashback as long as you don't run a given orifice way too hard, and are using smaller torches. The real bad news is no one way valves since running the O2 into your Acet can could prove disturbing. But as far as I know the Flashback thingies I have protect against both. Some of the better regs also have one way valves in them, I think...
Reg needles don't even need to be used. According to White, the classy way to set up the torch is to open the handset valves all the way (without loosing the packing) Then open the Acet reg until you can feel the gas coming out of the torch on your cheek (kinda creepy). Then remove torch to safe location and spark it, never use a lighter or match. Then adjust the O2 reg until you get your flame just as you like it. Then boost both a little until the flame is noisy. Then bring the flame back to where you want it with the handset. This ensures not over running the head. Also ensure lowest pressure in the system, which is good all around. This is where you will find out if your regs are good and can hold a steady pressure. It is also important to use enough orifice, because if not you will probably be running the torch hotter, and get more pops. When set up as described one can just turn both handset knobs to equal open and spark both fuel and O2 at once, for fast starts. This is how I learned to do it from small torch videos, your mileage may vary. I certainly like the regulator setting.