Lip filler migration is definitely something that happens, but it's much less common when you go to an experienced injector who uses proper technique and appropriate amounts of product. Migration typically occurs when too much filler is injected at once, when it's placed in the wrong plane or depth, or when someone gets repeated treatments without letting previous filler fully dissolve first. Some people also just naturally metabolize filler differently or have tissue characteristics that make migration more likely. The key to preventing it is being conservative with the amount of filler, especially if you're new to it. It's much better to start with a smaller amount and add more later if you want than to overfill from the start. Make sure your injector is placing the filler properly within the lip tissue itself rather than just on the border or too superficially. Also, avoid getting touch-ups too frequently - give your body time to metabolize the previous filler before adding more on top. If you do notice any migration, it can be dissolved with hyaluronidase, so it's not permanent. But honestly, if you choose an experienced, reputable injector who values natural-looking results and doesn't push you to get more filler than you need, migration shouldn't be a major concern!