How much do fillers migrate?

Be sure that you have a good and experienced injector to avoid negative outcomes of filler. A Board Certified Facial Plastic and Reconstructive Surgeon would have intricate knowledge of the anatomy of the facial structures and placement of injections to create the intended, natural looking results desired while mitigating the chances of a negative outcome.

You are absolutely correct.
Fillers in the hands of inexperienced injectors can cause migration, blindness and skin necrosis.
Proper knowledge of anatomy and anatomical landmarks can minimize this complication.
for eg, fillers injected in temples can migrate to your cheeks because the layers of the face are all connected.
Please ensure that the injector you have chosen is experienced and a medical professional.

Fillers generally do not migrate. It is important when having a filler treatment that you select an experienced injector. Your injector will help you select the appropriate filler for the area you wish to have treated. The injector will also be skilled in proper techniques to give correction/enhancement while avoiding migration.

In general fillers do not migrate. The trick is to place them in the proper tissue plain. The other trick is to knowW when not to use them. Because certain areas do not have the surrounding soft tissue support to contain them. And, different classes of fillers are placed either more superficially or deeper. Have this type of discussion with whomever you choose to do your fillers assuming you are a candidate for them.

Fillers do not migrate if placed properly by an expert injector. The problem is that a great many of the people doing injections are NOT expert. They place the filler in the wrong place and it "seems"to migrate. I have been using fillers 30 years and have never had them "migrate" where I did not put them. Make sure you see someone who is an expert in using fillers and the area where you wish them. Just because they have been injecting for a number of years does not make them an expert.