I started diving doubles in order to do tec. I pursued tec in order to generally improve my overall diving skills, and maybe go a little deeper and stay a little longer (IOW, no plans to dive the Doria at this point). As I noted in a separate post, I suggest that anyone thinking about tec in the future consider setting up doubles and diving them a lot, well before starting tec (if that is where you might be headed).
There is a bit of a financial issue, of course. But, it sounds like you have been in a position to set up much of your future tec equipment (eg, BP/W, drysuit) already, and an additional investment in several tanks may not be out of the question. Before tec, I was diving single E-7 120s (had two of them), as well as an AL80, and had a AL40 pony. I set up my 80 and my 40 as deco bottles for tec, and doubled my 120s, which has left me without a good tank for single tank deeper dives (>100'). Taking down the doubles to dive the tanks as singles, then reassembling them for doubles is just not very practical, and I am enough of an air hog that an 80 is not functional on NC coastal wrecks. So, I am now looking at adding a couple of 130s to dive as singles, in those situations where that is all I want to dive. 'Ka-ching' goes the cash register, I guess!
Seriously, the bottom line is that, if you are thinking about tec, you may want to go ahead and set up some doubles (AL 80s, or steel 95s, or steel 100s, or even 130s) now, and possibly invest in an additional good single tank (a 130 for instance) to have flexibility. At least, that has been my experience.
>>My thinking is that the more diving I do in doubles, the more I'll have the skills ingrained when I get to tech even if it's not for a while. <<
Yes, yes, yes! I believe you are thinking along optimal lines. Kudos.
>>So, if all my dive buddies are diving singles with recreational (non-DIR) setups, is moving to doubles a bit overkill? <<
Not necessarily. I will dive my doubles on what is a single tank dive for my buddies, just to keep working on developing doubles experience. So, I come up with them when their air gets to the turn point, and I just don't change tanks between dives when they do.
>>Should I save the move to doubles for when I have a more definite timeline for tech, and for when I start diving with others that are diving doubles?<<
As you might infer, I suggest you not wait, if there is even a reasonable chance you will pursue tec. Tec training is a good experience - humbling, challenging, frustrating and rewarding. Being comfortable with your equipment when you start may well tilt the scale more toward the rewarding and away from the frustrating.
I hear there might be a few that dive in Monterey.... there's might even be a T2 guy living in LG
