Do I need more filler over time to achieve basic results?

Yes, and no.  Fillers add a bit of collagen to the skin so a year after the filler is placed, you might be in a bit better place than when you started.  On the other hand, we all continue to age and may need more product over time to correct signs of aging.  But fillers do not make things worse.

This is a common question I receive, so you're not alone in having this fear.  Most conservative injections of dermal fillers will not stretch the skin to any long-term degree.  Your skin is an amazing organ which will adapt with time, so as the fillers begin to "dissolve", your skin will naturally tighten, especially if you're combining injectables with other treatments (skin care products, lasers, hydrafacials, Skin Pen, etc.) to maintain healthy and vibrant skin.

We use exclusively Allergan products which do not stretch the skin, as these fillers are designed to increase voloume, fill in loose skin, and plump up skin.  Take into consideration the aging process is still a factor,  and sometimes people want more after getting use to fillers.  Best Wishes

No, there is no evidence to suggest that fillers cause the skin to stretch. Actually, there is some evidence to suggest that HA fillers may actually stimulate some collagen production. With time, however, you may require more fillers as you age and lose collagen, elastin, fat, and bone. 

Although it used to be thought that there were only a couple of collagen stimulating fillers, recent research has shown that most hyaluronic acid fillers stimulate new collagen. This means that some of every filler injected gets converted into collagen, which means that the next time you fill the area the amount needed to achieve the results achieved the last time is less than it was then. Although you continue to age, the residual effect from the last injection seems to over compensate. I have even had several patients get to the point of not returning for refilling some areas. When filling is done properly, the tissues are not stretched, only refilled.