As it is, certain SvCs that are also delivery centers have a 2nd shift with people routinely working until 11pm. I could envision 24/7 coverage at some point. New car delivery prep does not have to be done during daylight hours, presuming there's good lighting. Getting more out of existing SvCs would not hurt insofar as serving areas of DENSITY as well as those constrained by DISTANCE.
Areas of density aside, I wouldn't mind seeing more SvCs at least along heavily traveled corridors. Pick a city along I-40 between Flagstaff and St. Louis, for example. Most of that area today is served by rangers, who don't work weekends at least as of last October. It's an interesting challenge, really - on the one hand, you've got Sales & Marketing attempting to drive the bus, and then you've got Service/Operations trying to keep the bus running.
In the end, X cars will be delivered, Y SvCs will be built ,and Z people will be hired to staff those SvCs. The challenge is the 4th axis - time.