I would like to know the effects and frequency of fillers.

My forehead has always been on the flatter side, so I’ve been self-conscious about it whenever I pull my bangs up or tie my hair back. I don't want a drastic change, but I would like to add a little volume to give myself a softer look. I became interested because I heard a lot of people talking about fillers, but after looking into it, I learned that there are various types of products and that the duration of effect varies. Does the duration of filler effects vary significantly from person to person? I am also curious if the duration differs between areas with little movement, like the forehead, and areas with a lot of movement, like around the mouth. I heard that fillers don't last forever after a single treatment but are absorbed over time; how often should I consider getting a re-treatment? I’d like to know if a first-timer can receive a consultation without feeling pressured, and I’d also like to know what needs to be checked before the procedure.