How far back should your brake lever go?

[Dead Eye]

Sounds like air in the system to me. Only other thing would be significantly warped discs (pushing pads out) but that would cause many other symptoms that you haven't mentioned such as knocking

Bleeding the brakes should only take 10-15 minutes and its easy enough to do. A section of clear tubing is helpful, but realistically you can do it without it, it just gets a little more messy

Failing that, my bet is on brake lines - if its still the original rubber hoses then they could be expanding due to the pressure or bulging in a specific place. If that's the case, replace them ASAP