Filler frequency... How often should I get them?

I am looking into getting fillers for my cheeks, nose, or chin, but I am confused about when the effects will appear and how long they last the first time. I am curious about the treatment cycle. I heard that they usually last about 6 months to a year, but for those who have actually had them done, how often do you need to get them refilled? I am also wondering if the frequency varies by facial area (cheeks, nose, chin) based on hyaluronic acid fillers. I am worried that getting them too frequently might cause my skin to loosen or lead to side effects. Please let me know if anyone is aware of potential side effects or prevention methods. I would also love to hear your experiences regarding how you managed maintenance after your first treatment and how you decide when to get re-treatments!