Post production has been a significant part of photography ever since the beginning of the medium. Back before digital, it was all about how you handled the development of the film and then the enlargement of your print, now it's about how you handle your digital files.
Post processing images seems to be one area where there is always room for growth. The more you learn about your own preferences and tastes, the more you will see how your use of post production tools will change. Post production doesn't necessarily mean you have to fix the image, though sometimes that's exactly what you end up doing, but rather processing the images allows your true creativity to flourish. It's the time when you get to decide how your vision will end up being shown to anyone else who sees your work.
I have found that no matter how many images I process, not matter how many times I think I've mastered the art of post production, there is always something new to learn. One of my favorite ways to expand my own horizons is to simply study other photographers. I don't necessarily have to like everything that they do, but gaining an understanding as to why they do what they do to their images is always a great eye opening experience. This video by Julia Trotti is one of the ones I've most recently watched as I continue to go about re-thinking about my own processing techniques. She has a very efficient workflow, which I definitely appreciated watching, plus she has several other great tips and advice to offer including a couple free presets which you can download from off her YouTube channel. Check it out!