Yeah, what he said. I'm closer to 50 than 40, and some of the languages I have worked with in the past are no longer in use, or at least not widespread use (then again, some of the software I developed is still being used 18 years later). I took some time out from development, in a business analyst role, and enjoyed that quite a lot, but not as much as I enjoy development, and after a few years I felt like I was kinda falling behind on the technology.
Having moved back into a development role, partly supporting old legacy stuff and partly doing new development in .net and C#, I am not convinced that I am happy *just* doing the .net work, and would love to have a good excuse to use python and other application or web frameworks. The more languages you learn, I believe, the easier it becomes to adapt to others. Or at least you get a better comprehension of their strengths and weaknesses.
If you are having doubt whilst still so young, you are either not really a natural programmer, or you have become jaded from being in a rut too long. Maybe you need to look into some of the open source projects out there in internetland, some of the apps, libraries and, for example web application frameworks, inspire me endlessly (mostly wishing I could get my employers to pay attention to them as well).
Do what you enjoy, all the better if somebody else appreciates it and pays you for it, but try not to get trapped into just using one toolset or language. Go for variety and always try to learn new ones when you can.