I'm considering getting fillers. How long do they last, and what is the frequency?

Lately, my nasolabial folds have suddenly become so noticeable, and I'm incredibly stressed about it. It upsets me because I feel like I look older every time I look in the mirror. So, I'm considering taking the plunge and getting fillers, but I'm really having a hard time deciding.

My friends recommend fillers, saying they dramatically change your look, but now that I'm actually thinking about getting them, I'm worried about side effects and whether the effects will last longer than expected. I'm curious how often I usually need to get fillers to maintain a natural look! Please also let me know if there is a lot of swelling or bruising immediately after the procedure. I would also appreciate it if you could recommend a good place in the Gangnam area!