Rob,
The company I work for has a lab that calibrates our wrenches.
But for a guy without that resource, where do you go??
The first place I looked was Google, check out "Team Torque"...they're so into it they even have a Torque University you can attend :bom_rolleyes: You ship your tools to them and they come back calibrated (hopefully not dropped off the UPS truck on the way back)
http://www.teamtorque.com/index.html
Here's another one...MicroPrecision:
http://www.microprecision.com/capabilities/torque_wrench_calibration.php
But I'm sure there are places near you that can perform this service. Our company specifies recalibration every year, and that assumes daily use. So I would think that we shade tree bike techs could probably go 3 years (just a guess).
The whole point being a torque wrench needs to be calibrated to be of any use. Might as well use a breaker bar and tighten til it smokes (then back off one flat) if the torque wrench isn't maintained.
In fact, there was a thread on Stromtrooper not long ago (I can't find it) from a guy who did the valves on his 650, and when he went to start it up, all the bolts holding one of the cams just popped off. After much speculation, he found that his torque wrench was clicking at 3X the amount he dialed in...those bolts were so tight they snapped as soon as the engine heated up.
Try a google search, or your local phone book for a service you can deal with.
Good luck!