I have a bunch of regs (Apeks and S'Pro). They all came out of the box and got put into whatever service I needed them for at the time (backgas, deco, stage). I don't differentiate between my deco regs based on what gas they will see. I pick one up, it goes on the cylinder that needs one. The odd time I need a single tank setup I'll mix and match bits and turn a deco reg into a single tank rig. If a backgas reg goes tits up then one of the spare deco regs gets fitted out for backgas.