How to make Restylane injection last longer?

Restylane in the tear trough area would will already last longer due to less movement around the eyes, up to 18 months 

Great question but there is very little you can do to affect longevity of fillers.  One thing you can do is to make sure you have a great result.  Under-treatment with less product than an are needs usually leads to needing to re-treat an area sooner than if an adequate amount is used.  Over-doing exercise can also break down filler faster in some people.

There are no foods or activities that will affect the longevity of Restylane placed under the eyes.  Restylane does tend to last longer under the eyes than when placed in lips or around the mouth though.