There are some one time use fasteners that are legit. Things with sealing rings or other special properties to them. Others though use the argument that they come with loctite on them and the end user is too dumb to clean and reapply loctite on reuse. Others don't have any rationale at all (except to get you to pay $27 for a special Screamin' Eagle High Velocity Special Inductive Thread Fastener because your old "bolt" suddenly isn't ok anymore.
Those l can agree l would change.
As for the others I thought it was more of a sales pitch
I'm a user of loctite ( blue) on my bolt fasteners regardless unless it requires ( red) I've come across fasteners working lose on my inspections. When I do come across one l remove it and blue loctite it.
There are some fasteners these days that truly should be replaced and not reused. Unfortunately unless you're a fastener engineer you have to rely on the manufacturer of your particular product to point them out. Like some have already mentioned, some companies go overboard and say to always replace some fasteners for the wrong reasons.
If you're dealing with a "torque to yield" fastener and application, yes you should replace the fastener. Look up elastic versus plastic deformation.
Jerry
Yes I'm familiar with elastic/ plastic deformation. As you tighten up the threads fold that tighten it up. That's where the little trick comes in on giving a sharp blow on the head of a bolt to shock the fold of the threads to help break it loose.
Also the torque to yield, as in a stretch fastener I agree are a one time use.
I always run a tap in a hole and clean the fasteners threads on a torque bolt before fastening it up to be sure of a unobstructed true torque.
Thanks guys for the input. I got more of a handle now on what really needs replacing and what doesn't
