Pick up a couple of inexpensive deflection style torque wrenches. They last forever. I have two craftsman wrenches that are older than me, and still calibrated at 0.

Generally, when there is a torque spec, it would probably be in your best interest to use a torque wrench. Even the performance of the bike (shifting, etc) can be noticeably improved using proper torque. You can also eliminate a lot of strange noises too.

That being said, I've only ever used one of my crank bolts. That is the only time I've needed it.