I second what eelnoraa said.
Let me explain what the annual service consists of:
Annual service is a preventative measure to make sure your gear is tuned up and all worn parts are replaced.
I dive a lot and service my reg annually. I also send my computer in to check it and clear out any grit that's stuck under the buttons.
Without my free parts warranty, the total cost would be at least $100. You usually pay for a service fee at the very least, then fees for any parts that had to be replaced (unless covered under warranty).
To keep your warranty for free parts or replacement of defective parts you'll need to service your equipment according to your manufacturer's specifications. This can be yearly or every 2 years. Read your manual(s) to figure this out.
- Some members on the board swear by annual service regardless of yearly use.
- Others go by the thought that you should service based on use, more or less.
ie. If you dive only 5 times a year, you can probably skip annual servicing (which would void some warranties), and service every 2 years.
However those members also state that you should know how to check your own gear to spot any malfunctions. As well as knowing how to detect malfunctions during your dive.
Turnaround time for servicing gear can take 2-4weeks.
With my BC I don't service it, unless it needs repair. The only things that need to be serviced on a BC are the bladder and the inflator. If the inflator is malfunctioning, it's usually cheaper to just buy a new inflator and replace it yourself. (All it takes is scissors, a ziptie, and sometimes a tiny punch/toothpick)
If the bladder is leaking then you can take it in for service.
Both of these things can be spotted easily.
- Just plug in your inflator to a tank and give it a test.
- For the bladder, inflate your BC as far as it will go and let it sit overnight. If the bladder isn't as rigid and full as you left it, then you have a leak.
As for storing you gear, if it's sitting in a nice climate controlled room such as your bed room, it should be fine. If it's in your garage, public storage, or an attic, it may begin to wear due to exposure.
At the very least you should check your gear before any dive trip, and then check it again during your buddy check. If you want to check it at intervals during the year regardless of whether you're diving or not then all the more to you.
The point is if you find something wrong during your check you should definitely service it.