303 stainless steel seems a strange choice. Probably chosen for its cost and machining abilities rather than its anti corrosive properties.
Personally I'd consider these types of regulators throw away items. At $255+gst they cost little more than what you would expect to pay for a service.
On the other hand my SP 109's are probably 40+ years old and thanks to SP's design ethos share many of the same parts as the new G250V so parts will be avaliable for many years to come.
What I didnt mention before was 1st stages.
I have always used SP MK20's and MK25's which are piston regulators. But more recently I have been using Apeks diaphragm 1st stages as well, which I think have the advantage of being sealed and there for possibly can be pushed longer between services especially if you are the type of person who does religiously soak them after use.
But really I think any quality 1st stage should be good enough. As long its made with good materials, spare parts readily available and the hose routing suits then it should be fine. The 2nd stage is what will determine how well a reg set breathes. And dont get hung up on mismatching regs. No issues having a Apeks 1st stage, SP second and aqualung octi...unless your service agent cant do all 3.
Having said all that.... I have 2 MK25's and 2 BA's I'd consider selling. They are set up for doubles but I can configure. I have a few other regs for sale too. SP D350, Mk2 MK5, 190. But I want top dollar for them all
Mind you this is/was a hell of a deal ( from a previous board member)... http://www.trademe.co.nz/Browse/Listing ... =521769508