I had my regs serviced about 4 years ago. I used them once or twice afterwards, then for one reason or another I didn't dive for 4 years. The regs have sat in my dive bag in the house all of that time. I now find myself going on a diving holiday and was wondering if my regs will still be safe? do the O rings 'dry out' if not used for a long time? Do you think I should have them re-serviced even though they've only been used twice since the last service?