Buying an older airplane

Hello community,

imagine you consider byuing an older airplane, e.g. a Piper from the Pa-28
Arrow series: is there an age (or a year of birth ;-) you would not exceed?
If yes, for what reason (e.g. may be that corrosion-protection was not usual
before that year, or that copper was so expensive, they used something less
conductive as a replacement)?

Thanks in advance for any help.

Regards

Kai Glaesner