Hickdive
Contributor
From what I have seen, the better shops will replace a few components that are not part of the normal regulator repair kit (usually only includes regulator dynamic o-rings), such as HP spool o-rings and dynamic hose o-rings which are rarely part of the service kit. All other o-rings should be inspected and replaced if a problem. Most of these are static o-rings which may last quite a ling time. (I am still using some that are over 20 years in service.) If the shop wants to charge a fair price for these additional o-rings we would be talking about $.05 per; but no extra charge would probably be a better business move. I have seen shops charge for Christolube used to lubricate o-rings. That can't be good for business.
Most kits come with hose and plug o-rings (certainly Apeks and S'Pro) and they get changed. Since I'm servicing the reg and not the accessories such as SPGs I wouldn't ordinarily touch them unless asked to by the customer. Of course any leaks from the interstage hose or plug seals will be detected in the wet test and, if necessary, I'd replace them anyway without additional charge. The cost is negligible compared to giving the customer a perfect reg back.
With SPG spools, if there was a leak I'd normally just show the customer how to do their own in future whilst swapping out the problem one. They usually end up buying a couple of spools for their spares kit so I get a sale and they go away happy with a little bit of extra knowledge for free.