As a maintenance business owner for 8 years, a store manager for 15, and now a store owner two things jumped out at me as I read this.
I have to say that what Curtswearing mentioned is one of my biggest pet peeves. At least once a week I took a phone call to trouble shoot a problem for someone only to have them tell me, "thanks, those guys at store xyz didn't know anything but it was cheaper there" or "no i didn't buy it from you but I knew you could help me." Better yet here's a phone call I took right before I left my managerial position. "Hi can you tell me about Sebae anemones? What will host in them? What are their requirements?" And on and on for about 15 minutes. Only to be followed with, "well thanks a lot, I'm at Petco and they have one I'm looking at for $20 and I knew you could tell me how to keep it." Or someone would come have us design a system only to go out and buy all the components somewhere else or online only to save a few dollars. System design takes time, which costs money. Thanks for wasting mine! I know this is all part of "retail" and as a store owner you have to suck it up and at least be thankful for your knowledgable reputation, but it doesn't mean its not wrong.
Also, I'd be skeptical of anyone who knows "everything." There is so much to know, the information is constantly evolving, and there are huge grey areas and lots of truly unknowns. Anyone who can't admit they don't know once or twice or never has too go look something up to be sure, would scare the heck out of me. I would always be asking myself....do they REALLY know everything?