Deflecting bar wrenches are usually accurate right out of the box and remain that way for almost all of their life
The clicker does wear over time and will click earlier but on most good ones it is replaceable .
Micrometer adjustment ones are almost never accurate and unless regularly checked go out of calibration very quickly because they rely on a thin spring .
If you want to have fun, go to your favourite junk shop, take 2 out of their boxes , connect them together set them to the same tension then see if they click together .