Can/should you re-use engine components?

12many said
I learned years ago with chain driven motorcycles that chains don’t stretch. I know it’s a term we all refer to and many may know it actually elongates, It’s the pins and rollers that wear due to inadequate lubrication so then they made versions with o-rings, then x-rings, special alloys, special grease etc etc. The sprockets teeth wear, get wallowed out because the chain gets elongated. Taking steps to deliver adequate oil to the timing chain helps. I drilled a hole in one of the cam retainer plate bolts (does it help dribble oil to the chain? no idea but people here said to do it, seems like a good theory) and the tensioners plate I’m running has an oiler tab directed towards the chain. I ended up reusing the Summit billet timing set (same as Jpar shows) on a cam swap a few months ago and noticed the chain had pretty much the same play when I first installed it over 4 years ago, WITHOUT the tensioner in place during degreeing.
The myth of chain stretch - MRO Magazine

Well, semantics. Is the chain longer when all the wearin gets done? Yeah it is so.......
IMO, it's not necessarily from a lack of lube, although I'm sure in some applications that might be true. I think with what we're encompassing "HERE" it's cheaply made parts. ......although I'm sure the extra heat from crappy factory chain oiling plays a role.

That said. There are mods we know how to do to our engines to get oil to the chains. Like on the slant 6 for example, we drill a small hole right through the end of the the galley plug in the front, providing pressurized oil right on the back of the camshaft sprocket. All the other engines have their tricks there, too. IMO, those mods are a requirement for any build now that we know the tricks to doing them. Especially, since 99 times out of 100, they're free.