OK, Reality check. I have 8 sets of regs for me and my wife. I'll take them in overhead environments (cave, wrecks, deco). I service them myself since I have no desire to pay the rates on 8 regs.
I have a very different philosphy with regs. First, I dive diaphram regs, most of which have the environmental kits. I also treat 1st stages and 2nd stages differently.
Simply put, my first stages are pristine inside when I have rebuilt them. They functioned flawlessly and were rebuilt only to ensure 02 cleanliness. I have never had to rebuild a first stage for reliability and I have several going on 3-5 years.
2nd stages are a different matter. They get dirty as they are exposed to the elements. From my expierence, 2 years or so is an average interval. I service based on need, not time.
Lastly, for those who throw the life support BS argument. My answer is quite simple. Losing a reg underwater is NOT life threatening. You have been taught how to handle this via Air share, CESA, buddy breathing and buoyant ascents. That's 4 options. Inconvenient yes, problem no.
For those who are agast, let me ask you this question, do you service your BC's, drysuits etc as well? How about inspecting lights, fin straps etc. Do you replace fin straps once a year as a 'preventive maintenance step to ensure safety'? I'd sure rather have a free flowing reg than lose a fin myself.