Here is a story to feed the discussion on when to service regulators.
My first regulator was a Mares, and I had it serviced faithfully every year, even though when I was a new diver I only did one week-long trip a year. After a few years, I became a DM and was employed by the shop I used. I learned then that they did not have a qualified Mares technician on staff, so whenever a Mares regulator came in for service, they sent it out to another shop which did. I didn't see anything wrong with that.
Working with the shop meant using the regulator more. I went on a shop-led trip to Thailand, and I had some regulator problems. This was my first diving since having had it serviced a few months before. They made some adjustments on the liveaboard to get me through the week. Back in the USA, the shop sent the regulator back to the guy for another service. It came back, and I took it to Florida for more diving. I had problems again, and a local shop again got me through that weekend.
Feeling that something was up, my shop sent it directly to Mares. When it came back, Mares said there was nothing wrong with the regulator itself. The problem was that it had obviously not been serviced for years--if it ever had been serviced at all.
Eventually we figured out that the guy they had been sending Mares regulators to for servicing was doing nothing more than holding onto it for a couple of weeks and then sending it back untouched. During the time I owned that regulator, it had happened 7 times.
