All torque wrenches go out of calibration due to use or abuse. I get mine done every 2 to 3 years. I pay for a basic calibration and I'm a tech I'm not paying for a cert which is only needed for aircraft ect.
If you don't know the condition of the torque wrench it's advised to get it checked and it wont cost much hell some guys would probably check it for free.
And to anyone that is wondering about how they do it, they use a device that measures torque and a screw that moves the wrench so when it clicks or beeps it gives you the reading if the wrench doesn't match you adjust the adjuster untill it does.
Snap-on actually sell calibration units, ranging from cheap to very expensive. The most expensive are mounted on a table/toolbox
Norbar sell a digital torque checker for workshop use just as a quick check to double check the wrench is in cal.