I showroomed 4 bikes over 3 hours at Cyclery USA in Riverside knowing full well I was going to buy two of them from that same business, but the store in Rancho Cucamonga instead. To reciprocate for their time in Riverside, I sent the gang four dozen chocolate covered strawberries and a postcard from Sedona. Hell yea I showroomed, but I also ride with those same dudes on weekends and drink lots of beer afterwords.
Nothing solidifies one's relationship with a LBS more than joining them on a shop ride and, like Mr. Bomb says, "hauling the mail!" You can buy 5 expensive bikes from a LBS, but if you suck at riding them, you won't get as much respect.
I have consumed so much bike stuff that I need vendors on all fronts to support my cycling habits. It's a case by case basis for me, but I usually go for the best deal be it brick and mortar or online. Usually my LBS (Cyclery USA in Rancho Cucamonga) would match an online price or come close enough to it that I readily pull the trigger. Kenda tires always from Jenson USA, unless I need the awesome ( and true to size) Bontrager XR4, which I will pick up from my LBS. Lights and battaries from Westernbikeworks. Backpacker also hooks it up, and they give freebie GOAT stickers! When I upgrade or replace parts, only my LBS will trickle down parts from my primary ride to my secondary ride to my Hardtail turned commuter for no charge! The catch is I show up on shop rides and bring beer...done and done! The occasional chocolate covered strawberries or bombers from the Kern River or Mammoth Brewing Companies also earn points, and it feels good to go into a shop and see yourself on the video monitors from a GoPro shop ride. Also, I have Trek Redshield [wear and tear coverage], which has paid for itself so many times over its just insane that I would consider buying a different bike without similar coverage, and only my LBS gets my drive train, brakes, and "worn out" fork stanchions replaced every two years. My LBS friends have taken good care of me indeed. A few of them even came to my wedding! Having said that, give me a coupon for wherever, and I'll shop there.
Near the office I have Helen's and REI close by, and both have come in handy for a mid-day parts replacement or tune up before an afternoon ride because I needed the work done same day before 4pm and they got 'er done! These two shops are usually utilized when I'm tinkering the night before a weekday ride and either break something or notice my spokes or cables are toast. I have taken coworkers to both shops for showrooming bikes, and to date no bikes have been sold from either merchant, but the service is definitely handy.
How about this for a LBS business model: Have one competent mechanic work the graveyard shift from 7pm (when all bike shops close) until 3am and a second mechanic from 3am until 10am so that (1) the service backlog gets completed sooner than later, (2) the showroom is always well stocked with fresh builds, (3) for those of us tinkering in the middle of Friday night for a big weekend epic and break something or realize our brakes or drivetrain is shot, we could go to the LBS at 2am and find salvation...for a premium price of course!