As has been mentioned already, why are you considering becoming a DM? The answer to that question will be the primary driving force behind your actions. I'm about your age and originally from your neck of the woods. Moved to DFW in 1999 because I got sick of the humidity and just the area as a whole. Oddly enough I didn't become a diver until I moved up here, mainly because of finances. I was young and working so my wife could finish up school, etc. etc. I've been a DM for about a year now and I've done more diving in the past year alone than I did in the previous 5. So yes as a DM you will definitely increase your dive count, even if just during your training. But figure if you're helping with an OW class, you're making at a minimum 4 dives in a weekend. So if you're looking to get more diving experience in, it's certainly a way to do it.
As for actual learning during a DM course....you might learn a little in the way of how to do things more efficiently, but you won't really learn much in the way of actual diving because for the most part you'll already know what you need to know just to complete the DM course. You don't really go through a DM course to learn/develop skills. You're supposed to have all of that worked out before you even start your DM course. As a DM, students look to you to be an example of what proper diving form and techniques should look like and many of them will try to mimic your actions. I sat in on a refresher course last week and the diver that was doing it told me near the end of the "class" when I was giving her a couple of pointers that she was trying to mimic me in the water. A little while earlier before we were descending for the last part of the class she had asked what she could do differently because she felt a bit out of control during descent and wanted to be more graceful the way the instructor and I were. I simply told her that when I descend, shortly after my head goes underwater, I transition to a horizontal position, which slows my descent and gives me more control. So while you may hone in your skills somewhat during your DM course, I wouldn't really expect to learn a lot, aside form maybe a little about field repairs of gear and little tips and tricks.
As for whether or not it's for you....only you can answer that my friend. I became a DM as a way to give back to the diving community I love so much. I've had hobbies in the past that I got into and absolutely loved.....or so I thought. But after a short while, the novelty of them sort of faded out. Diving for me isn't a hobby so much as it is a lifestyle. It's one of the things I'm most passionate about. And my wife will tell you, if you don't want me talking for hours....don't bring up diving! Okay I might be exaggerating.....a little anyway. But if you're doing it expecting to make money at it....you're doing it for the wrong reasons. If you're doing it because it's the next rung on the ladder to instructor, that's not a bad reason by any means. Just make sure you make the most out of it and get all the experiences you can as a DM. Engage the students. Although they'll have the instructor to ask questions, they'll more often come to you because you're sort of the middle man and they identify more with you than they do the instructor because in a sense you're more on their level, as strange as that may sound. You're not as much in the authoritative position as the instructor so you're more approachable. So use that to your advantage and make friends with the students you help teach. Never know when one of them may come back and ask you to lead an all-expense paid trip for them to who knows where. I've seen it happen.....just not for me.....yet. Also, whether you're planning to push forward to being an instructor or not, get to know the instructors you work with. Get to be the DM that stands out in their mind....the one they look forward to working with. That, too, has its benefits.
My experience as a DM so far has been about 98% positive. The 2% that wasn't was mostly my fault because I lost sight of why I became a DM to begin with. Well, one experience anyway. The other involves diving in 50 degree water in the middle of January with ****** vis, new students, and one in particular that honestly probably shouldn't have been at the lake that weekend in the first place. I ended up having to drag him up from the bottom, literally laying in the mud panicked out of his mind on the second dive. Even that wasn't a horrible experience, as my training pretty well took over and everything went pretty smoothly. But a few months back, I spent two weekends DMing an OW class, the first weekend in the pool and then the following weekend at the lake. It was actually my 10 yr old son's OW class and I didn't really want to DM it for that reason, but the shop needed a DM so I agreed as long as I could be very hands-off. The next weekend my son ended up having to cancel because he wasn't quite ready for the lake yet so I ended up going out by myself to help the instructor. Ended the last dive, got everything put away, students left, etc. etc. and it came time to see what tip money I'd ended up with. $40. Two weekends worked, 1.5 drive each way to the lake the 2nd weekend, money spent buying donuts, etc. for students, gas, drinks....it cost me money to help an instructor teach 8 students how to dive. He got paid fairly well (to keep it somewhat anonymous I won't give numbers) and I got stiffed. It left a really sour taste in my mouth and I haven't DM'd an OW class since then. Not so much because of that as it's just really cold right now and putting new students in 50 degree water and asking them to perform tasks that are still somewhat foreign and challenging to them just isn't what I believe to be a good teaching experience. But getting stiffed on tips for two weekends worth of work didn't really help. So like I said if you're looking to make money as a DM, it's possible...but very very unlikely.
So now that I've essentially written a novel, take this information for what it's worth and make your own decision based on YOUR reasons. Being a DM has definitely not ruined diving for me by any means. If anything, it's actually made it more enjoyable for me because I get to share it with other people and I get to help bring them into the underwater world I love so much. Even with the ****** visibility, ****** pay, cold water, and sometimes thankless efforts, diving continues to be something I love, something I'm passionate about, and if I had it to do over again, I'd still become a DM. As fate would have it, I'm about to push ahead to Assistant Instructor. Hope this information/advice helps with your decision! If you have any questions, feel free to shoot me a PM. Happy to help!