Depends on the part.
When the bushes went in the 965's lower control arms, I bought a complete new set of arms since the labour charge for doing an R&R of the arms and changing the bushes would end up more than the new arms. So I kept the old arms and when the bushes in the new arms are shot, I'll press out the bushes in the old arms, replace 'em, and swap the old arms back in.
Basically, I keep old parts that can be easily refurbished.
Old water pumps, worn/cracked brake rotors etc, to to the tip or Simsmetal.
(That said, there needs to be A Reckoning around here - I have too much surplus).
