Dudes. Forgive me. It just all seems so crazy.
To recap.
I want a reg that's going to last me 10+ years. As an instructor. 5-6 dives/day, 5-6 days/wk. Tropical salt water. Chlorine pool water. Shallow depths. Warm waters. Nothing too crazy. Just need something that's going to be reliable. Never be a hassle. Always be there, ready to go to work with me. Something I can service (shouldn't be a problem). Something I can get parts for. Something I'll ALWAYS be able to get parts for (a reg that's already out of production??). From a brand that isn't going to go out of business or be bought out anytime soon (like 50+% of the scuba companies out there right now, over the next 10 yrs). Parts won't be super expensive. Etc.. etc.. etc. You get the drift.
And I'm telling you that money's no object. As long as it comes from a reputable scuba company.
And you're telling me that some 50yr old reg that I have to buy from eBay-ish vendors... because it's no longer made new by anyone. So I'm not going to get my discount. I'm certainly not going to get parts for life. I'm certainly not going to get any kind of guarantees, or warranty's. And the closest thing to this reg is.. currently.. the Aqualung Core, a crappy version of the Legend that we present as our cheap-skate reg at my shop.
And I'm going to be diving for a shop. Working for a shop. Somewhere out there in the tropics. Diving a reg that my shop can't sell to customers. ??? Supporting my shop in that way.
I mean. wtf...
What are you wanting to do, teach scuba or be a salesman?
You seem to be really buying into the hype that surrounds regulators. There is no "best" except in arguments about regulators. There are many excellent regulators that all do the job reliably and with good performance. The "best" argument is about narcissism and salesmanship. Not about diving or teaching others to dive.
What you have now (legend) is a very high performing, extremely reliable regulator that will work perfectly for you. There are many others that would also work perfectly. I would not be too worried about the environmental seal or about the differences between piston and diaphragm regs. In warm, clear water, they all work great.
It may be practical for you to own a different reg set for use in the pool; chlorine is really tough on plastics and metals. If I were teaching in a pool quite a bit, I would use an inexpensive reliable simple reg like the SP MK2, an older conshelf, or an older sherwood. Many instructors simply use one of the shop's rental regs in the pool.
Regarding older regulators, the truth is that regs have not really improved in many years, and it lots of ways have actually regressed as companies look for more ways to lower manufacturing costs and maximize profits. I could easily buy any regulator I want, but what I use for cave diving is an old set of MK10s with old 2nd stages (D300-balanced/adjustable). I paid less than $150 for all four stages. In OW I use a MK5 (even older and better than the MK10) and any number of old 2nd stages that, IMO, out perform anything current that I've tried.
When I think of diving all day every day in a tropical climate, one big issue that comes to mind is drymouth and dehydration. This is where the old metal case 2nd stages, with less aggressive venturi assist, can really shine. You trade a small loss on WOB numbers (test machines don't get drymouth) for increased comfort and enjoyment, again, in my opinion.
When I did my DM years ago in Roatan, by the end of the summer several of the instructors were asking for old metal SP 2nd stages; I ended up leaving a few there as gifts.
One advantage of some of the older 1st stages is simplicity. They are easy to rebuild with very few parts, and are designed to go a looonnnggg time between rebuilds. This can come in handy if you're living in the tropics and diving all the time.
There's really no reason to spend a fortune on a regulator unless you want to spend money, which many people do. I don't think a titanium regulator is worth it when there are literally thousands of brass/chrome regs that have clearly lasted 50 years or more. The titanium regulators weigh a little less, which would be very important if you were diving at the top of a mountain and had to carry all your gear up.
Many of the best DMs and instructors I have met over the years in the caribbean couldn't really care less about what brand of regulator they're using. They're considered tools; whatever works is fine. It's a refreshing attitude!
Most importantly I hope you have a great time diving and teaching diving in a beautiful location.
