I suppose you're right about the LBS. Not so sure about optimal pressure. It seems to me that flats have way more to do with road conditions and dumb (bad) luck. Glad your luck, or pressure maintenance has worked so well for you so far. But, yeah, that's coming from someone who watches his tire pressures. If you don't ever use a gauge or otherwise ride with tires with way too much or too little air, you are kind of asking for trouble.
As for Slime and the LBS, it may be just as valid to say that Slime will keep you out of your LBS as often, if you even use your LBS for tire maintenance.
They don't call it Slime for nothing, but anyway, it's never been particularly nasty when I've had to deal with repairing or replacing a Slimed tube.
TT