Yes, you should NOT store a click type torque wrench with tension set.
Also, make sure you use a six point socket.
I don't let tire stores tighten my lugs. I do whatever I have to do to see that I tighten the lugs myself. I have even taken the wheels off, thrown them in the back of my truck and taken them to the tire store, then put them back on myself.
Where I usually buy tires, they see me coming and politely get out of the way. They'll jack the car up and they'll even put on a wheel and start the bolts for me if I'm buisy at another wheel. I currently have a set of six year unlimited mileage Michelins that I bought from this store. They require that they rotate them every 7,500 miles. I drive in and do most of the work myself. They sign off the rotation in the log book and I'm on my way.
I use the short MB lug wrench to "torque" the wheels. I snug them evenly in the five pointed star pattern, then with the wheel on the ground, "torque" them with the lug wrench evenly. I have never warped a rotor with this procedure, and they're always tight.
I bought an extra long wrench from Griot's with a nice rubber handle. It is so long that it's awkward, so I put it in the back of my daughter's car. The extra length is handy for someone under 100 pounds.
I have some anti-sieze compound with copper in it. I use it occasionally on the bolts, so there is always residue on the threads.