I'm going to rephrase my question. I had an electrician come out and replace my neutral wire in the attic that went from our bedroom light to our hall lite. I just want to know why it needed replaced. Do wires just go bad or could it be from overloading? We have fuses and nothing blew. The wire didn't show any signs of being chewed on etc. It was completely intact too.

Greeting again. Instead of opening a new thread, please just use the "Answer this question" box. That way everything related to a question stays together.

Insulation on a conductor can fail because of a myriad of reasons. Since this conductor is in the attic, my guess the insulation or the conductor failed because of heat issues.

If that were the case, I would have replaced both conductors, not just the Neutral.

If the Neutral was for a Multi Circuit(2 circuits sharing 1 neutral), if on both phases is OK, But if your Electrician found that the 2 hot circuits were on the same phase than the neutral would carry up to the total of both, up to 40 amps on 2 20 amp circuits. And the Neutral would be the only conductor overloaded, and needing replacement and he would place both circuits on opposite phases.
If the neutral was damaged from a loose connection, it could be only conductor damaged. Or replacement was because of lack of enough wire in the box after stripping back for a new connection.