How true is it, that the longer fillers remain in the face the more they stretch your skin long-term?

No, once fillers resolve, the face will go back to its normal shape. These fillers (voluma, restylane, juvederm) and Sculptra can be used to create volume and contour in the face. Implants or fat are alternatives. I recommend getting a formal evaluation with a facial sculpting expert. Best, Dr. Emer

I disagree with this statement. Fillers have little to no permanent effect on the skin. The skin has a remarkable ability to stretch and contract. Let's remember, the effects of fillers create subtle changes to the contour of the face. These changes are too small to have a lasting or permanent effect. 

Dear Mariusses,your skin is very elastic and it tends to go back to the same shape as it was prior to fillers. Make sure that your injector is board-certified. Daniel Barrett, MD, MHA, MS 
Certified, American Board of Plastic Surgery 
Member, Am. Society of Plastic Surgery

Hi and thanks for your question. I have to disagree with your surgeon. The fillers are excellent treatment for volume loss and soft lift. All HA fillers wears off in few month and your skin will return to its prefiller situation also the aging process never stop.Sculptura is a very good collagen stimulator and helps naturally your body to build up the volume loss . 

Thank you for your question.  I have to disagree with your surgeon - well-placed fillers do not significantly stretch the skin, and in any case, the skin has a remarkable ability to recover from stretching, particularly on the face.  As your filler wears off, your skin should essentially return to normal (minus any interval changes due to the normal aging process that would have occurred anyways).  Please make sure you are seeing a specialist from a core cosmetic specialty (dermatology, plastic surgery, facial plastic surgery, or oculoplastic surgery) for your treatments.  I hope this helps!