As someone who's been taking photos since the mid 1980s, I can tell you that I've purchased gear with two different mind sets. One mindset is the one where I buy gear because I think I might need it. The second mindset is one where I have come across situations where my current set of lenses just could not allow me to get the type of shot that I wanted, so I used that to guide my buying decisions. The 1st mindset has led me to buy stuff that I've used a couple of times and then put in my closet for eternity. The 2nd mindset has let me to buy gear that I've used a thousand times and wouldn't leave home without.
So let your experience guide you. If you use the 18-55mm kit lens and you like the results, then keep it. If it doesn't meet your expectations or needs, then sell it and replace it with some that does. Maybe you need a lens with a larger aperture because you want to blur out backgrounds. Maybe you need a lens with image stabilization. Maybe you need a totally different focal length. Maybe you need all of the above.
Listen, no one is going to tell you that the 18-55mm is a great lens, because it isn't. But on the other hand, it's not bad either. It's designed for general purpose photography which is basically comprised of family shots, landscapes of where people visit and photos of friends along with other miscellaneous stuff like the desert dish at the fancy restaurant. Once you get a little more serious about photography and as result increase your diversity of subjects, that's when the 18-55mm quickly becomes inadequate. So think about your photographic experiences and if you discover that the 18-55mm is just sitting in your bag gathering dust, or it's somehow preventing you from expressing your vision (i.e. getting the shot the way you want when you want) then sell it and get something else.