Electrical vs. Mechanical Gauges

Yes it was awful and I do agree copper can crack especially if not installed correctly but if done right it can last longer than the nylon tubing they send with the gauges by at least double the life. When I first started working on cars I saw many 50's and 60's trucks that used the copper line last well into the 80's and 90's. The braided lines like Redfastback mentioned is definetly the best.

If I do use copper line I coil any stress areas around a 1" piece of pipe 6-8 times to relieve stress.

Interesting to hear that one, and I don't doubt you can make it last longer than nylon. There's some types of rubber that I suspect would hold up pretty well.

By that last line, do you mean that you coil the line into a springlike shape, like the loops in brake lines?