I found this info on torque wrench's
Some of it is interesting.
1.******Storing your torque wrench.
When a torque wrench is in regular use it does not need to be wound back. However, when storing a torque wrench for an extended period of time, users should always wind it down to the minimum scale setting and NEVER to zero.
*A fully loaded torque wrench, left in storage for a long period, can cause a ‘set’ in the spring, causing it to weaken over time. On the other end of the scale, by completely off-loading the spring, other components within the wrench may move fractionally relative to each other. When you reapply spring compression the orientation of these components can change, therefore affecting accuracy. All in all, it is better to leave a bit of compression in the spring while in storage.
2.*****For accurate results, one click is enough
Users often allow torque wrenches to click multiple times, without being aware of the additional torque being applying to the bolts. Operate your torque wrench in a smooth and steady manner and remember that one click is enough.