As ssgsnake said, a sub-ohm tank is gonna drink juice a lot faster...but that's why the flavor is so much better, too, and it will be hard to go back. You can expect to spend 7 times as much on retail juice (buying daily vs weekly), or you can get into DIY juice, and spend a lot less than you were on your 1 bottle/per week. About $0.04/ml for DIY juice.
Avail is the only national chain store that I know of for vape. Very corporate work environment, I'm told, but I've never been in one. I try to stay loyal to my local vape shop, but after hearing the radio advertisements for Avail, I do want to swing in sometime soon and check out their goods. Hopefully they have more in stock....local shops here have all cut way back on the amount of merchandise they carry.
ETA: Hit up Avail today. So-so. They had some good stuff, just not much of it...I expected a better hardware section. Didn't try any juices, not enough time. Ended up picking up a Cleito 120 at my LVS instead...pretty nice so far (I got it all of an hour ago), the coil runs at 100-120w...pretty decent vape. Have to buy the rebuildable deck separately, though.