I started out with PHP, got whatever job I could which involved Access and VBA, then VB.NET, then C#... now I use JavaScript, Python and occasionally Ruby.
That isn't to say that you should know six different languages. But you should know programming well enough that you can apply your skills wherever you need to.
Really? If you don't randomly flit from fad to fad you are "doing the wrong thing"? What if I made a good choice 15 years ago? Should I have stopped using postgresql simply because I chose it so long ago?
That wasn't what I suggested at all. My point is that you shouldn't be so focused on one language that you can program in that and that only. Even just being bilingual is a massive step forwards in overall programming skills rather than ASP.NET skills, or PHP skills, or...
Obviously I can't tell what you meant to say, but it is what you did say. "If your thirteen year old technology choices are still having an impact today, then you're doing the wrong thing regardless". My thirteen year old technology choices are still having an impact today. You explicitly said I am "doing the wrong thing". I believe that is incorrect.