How many times can u visit a hifi store before it annoys the store if u plan on a purchase

There are plenty of people that have no intention of buying and these people don't care how much of your time they consume. 

"Knob twisters"

"Tire kickers"

"Gear gawkers"

"Lookie-Loos"

Good sales people know who you are and see you coming. Don't be surprised when they don't return your calls. It's YOU who is the problem not them.

I always bring cookies for the crew....each time.  Or something.  It should be a bit social.  The exchange meant to be enjoyed, not endured.  I've even taken microbrew.  But then, that's just me.  Cheers

Completely dependent on the store and your personality. 

Are they opening the doors just for you or is it normal business hours and they are sitting there whether you visit or not?

If the latter then don't worry about it.

If you chew your gum loudly, just once. If you eat your noodles with your mouth open, you will get kicked out right away.