How many times can I reuse them? I have a lot of these on my street car suspension that I make adjustments to now and then - caster, camber, toe, pinion angle, etc.

If they still have good drag to them I will use it...
but if you can turn them on 1/2 of the nylon with your
fingers... get new ones.. I use a lot of them

Where I work, we can reuse them once. After that, throw them away. No sense in reusing something that cost very little, when it's holding a important part of the car together.

Technically, the decision to reuse a lock nut should be based on a "prevailing torque" test. IOW, the torque required to spin the nut before it starts to clamp the components.

There are charts that show the minimum prevailing torque based on diameter and the type of locking device.

To be honest... if its a suspension part that isnt
going to be tightened so things move... I'd put a new
one on each time... but if its going to be tightened
tight then I check them.... I have a drawer of each
size of 1/4, 5/16 and 3/8... but on any big stuff or
fine thread I have to buy them.. sure isnt like back
when I was working

my opinion on suspension stuff, if unable to use normal nuts with lock washers, is to use the "deformed" style nut, or castle nuts and cotter pins. i usually have to resort to drilling grade 8 bolts for the pin [if used with castle nuts] as well as cutting off of excess thread after i obtain a bolt with the suitable shank length. [no matter which nut is used] i don't like to use a bolt with too short of a shank that lets threads in the pivot area. i realize that those "deformed" style of nuts ruin the bolt threads, but i would rather replace the nuts and bolts during routine maintenance than have them come loose at an unfortunate time. just my opinion and what i feel comfortable with. what i really don't like to see on suspension fasteners is stainless bolts with polished heads. number one, if the head is polished, how do you REALLY know what grade it is, and number two, is the galling tendency stainless has without using something on the threads to prevent that from happening. and even if you use loctite or anti-seize [some even suggest using pepto bismal], there is still a nagging feeling i get that even though it feels tight, did it gall at the proper tightness, or will it gall upon removal and create a real problem removing the fastener[s] ? again, just me.

Those "deformed" nuts, are called stover nuts. Stainless hardware has no place in a race cars suspension IMO.

I'd go with castle nuts and spring clips if you need to remove it often. Used them on the sport bike for things that needed to be safety wired but removed often.

The safety wire in that pic is only a teather correct?

IMO nylon lock nuts are too light duty for a race car. I relate them to household use where they won't be subject to much heat and vibration. I reuse them around the house but would not use them on my cars.

Metal lock nuts should be used on cars that are higher than grade 2.

Well all of the airplanes that use them must be light duty? The metal lock nuts are typically used in high heat applications where the nylocks are used in areas that are not subject to rotation. If the bolt is subject to rotation, ie the bolt turns in its application, then you use a castellated nut.

All my suspension hardware is grade 8, all big stuff ( 1/2. 5/8, 3/4 on 4 link and front control arms ) and all nylon lock nutted. Guess it's time to spend some $ at www.fastenal.com.

I use G8 SAE thread and nylocks everywhere. No top locks, no lock washers. If the bolt is in double shear, (4-link, lateral link, motor plate with a limiter), and not subject to high stretching loads, I will use a shorter bolt and the short nylocks. Weight. No hardware store, cheap stuff.