What happens if you don't get fillers (Voluma) redone?

I am a 22 year old with a flat/thin face who would like to get 1 syringe of Voluma for a subtle cheekbone. I have heard that the filler gradually fades away to your face's old state, but this sounds too good to be true. I just want to make sure the skin won't stretch of look strange if I decide I do not want to get the filler redone (for either aesthetic or financial reasons). I imagine that I will metabolize this quicker since I am a younger patient. What should I expect if I don't get it redone?