Braided fuel line questions

They typically do not 'wear out' with normal use - I'd expect them to last the life of the car. They can be damaged however - such as, if you try to snake them through a hole without a rubber grommet protecting it.
I'd ask him why he feels that they should be replaced...was there a leak? Faulty installation is the most likely culprit in that case. And be advised the the ends and elbows are very susceptible to galling.

Well, normally the braided lines will last quite a while. However, with these new ethanol blends that are being forced upon us, the life span of fuel systems isn't what it used to be. Hot Rod magazine did an article detailing this problem within the last couple of months.