How Long Can Open Restylane Last if You Are Getting Touch Ups?

In our practice, we don't save syringes. There is a finite chance that your syringe could be mixed up with that of another patient, transmitting disease or infection. This can occur due to natural human error even if samples are labeled. If the doctor doesn't save syringes, that chance is zero.

Generally speaking, it's safer not to save your syringe as the risk of contamination significantly increases.

While we have not read the study Dr. Weiner references (that states the product will remain sterile for 9 months), we have a policy at our practice of not saving syringes.
The first reason for this policy is the possibility for contamination. We are not in the business of storing partially used materials like this but rather injecting our patients. We encourage patients to use all of the product in the syringes and dispose of any product not used.
The second reason we do not store syringes is that we would have to charge for our time to inject the leftover product the next time around. Once patients understand and take into account that they are paying for the product and our time, they realize why we would have to charge for a follow up appointment.

Any physician or less who is saving Restylane is probably cutting corners elsewhere as well. The practice of 'saving' fillers is one that is fraught with problems ranging from the potential of mixing it up with other product to becoming contaminated. Even if it doesn't have any of these issues, just the concern of either of these is enough to keep most reputable physicians from doing this.
Those that don't are skating on thin ice and if they are willing to flaunt the rules and recommendations for this, they are most likely to do that for other things. You don't want to put your safety in their hands.

We also discard any remaining products once they are opened - I don't believe the companies advocate saving and reusing products and there is no safety data to advocate doing that. The issue of possible contamination is not worth saving several hundred dollars.This is not something that is practiced in the U.S, 

It is not recommended to "save" syringes. On occasion, if a patient uses less thatn 1/2 of a syringe, I will carefully label it and seal it and keep it available for about a week or so to allow the patient the opportunity to return if they think they need more filler. But, it is not my common practice. I usually use the full syringe on the indiviudal patient.

It is not our policy to save syringes.  In most cases, we are able to find other areas of the face where injection of Restylane would be useful, so that we do not waste material. 
Also, Restylane and hyaluronic acid materials such as Juvederm tend to dry out pretty quickly after opening (days to weeks).

Each syringe contains 1 cc. This is a very small amount and I think it is much safer not to save the product and use it every time it is open. An expection might be a delay or a day or two for some unsual reasons. It is the potential for infection or switching syringes that worries me. Good Luck!

There has been a study on the sterility of opened Restylane. The study concluded that an opened Restylane syringe stays sterile for at least 9 months.

Restylane is FDA approved to be used once opened. I don't know of any studies that have looked at the longivity of Restylane once it has been opened, but would suspect that if opened but recapped and stored properly, it should last at least until the actual expiration date posted.
Safe to follow FDA recommendations.