What is the reliable life span of galvanized &/or copper pipe?

I am looking to buy an older (lower priced) home in a suburban area near Detroit. I am running into many of them which have galvanized pipe. I don't want to buy into potential plumbing problems or the expense of re-piping. So, I am trying to get a better idea whether to reject homes with galvanized pipe altogether or am I being overly cautious?

Second question: When did wide spread use of galvanized pipe end & when did wide spread use of copper pipe start? This will help me to define the age cutoff of how old a home I should consider - as well as which to reject.

Richard