I'm pretty sure the Torque is adjusted by tensioning a spring inside the tool, So yes, best practise is to wind the tension back off after you have used a Torque Wrench. It'll keep it more accurate for longer
Also, you IDEALLY shouldn't use a torque wrench for undoing bolt's, that's where a breaker bar would be better.
I need to get myself one of those Nylon covered socket's too. Cheers.SS