How often does filler migrate?

Not only can hyaluronic acid fillers migrate they can also expand as they break down and absorb water. I have seen many patients over the years come to me for a second opinion after getting fillers placed in the past. The most common area of migration and swelling I see is from the NLF to the adjacent cheek area. HA fillers are a gel that can be squeezed in this high pressure area laterally to the lower pressure cheek area. Amazing how much better a person looks after I dissolve the filler lateral to the NLF. The most common area of delayed swelling I see is in the area around the eyes. I have dissolved filler in this area that had been placed years earlier. I have also seen migration from the upper lip to the area above the lip. I call it the Marge Simpson look. 

The video you are referring to is a series of MRI studies showing residual filler in patients who report not having injections in many years.  Above the lip is a common area we see filler migration in patients who have been treated multiple times over the years. However, this could be related to original product placement versus migration. 

I appreciate your concern. However, it is very rare for filler to migrate and if it does, it typically occurs within days after the injections, not months or years. Research has shown that these fillers bind with the tissue in the treatment area quickly and at that point, they will not migrate to another locations. Hyaluronic acid fillers only last a few months in most cases, as the HA is reabsorbed by the body over time. 
When you schedule your filler treatment, make sure it is with a board-certified dermatologist who has expertise in these procedures. With the right filler and an experienced providers, you should see very good results from your treatment without worry over possible migration of the product.