Every hunter in Solo Leveling has the right to retire, like civil servants who spend half of their lifetime working in different industries. It’s a natural outcome, especially for those hunters who wish to step away from the dungeons before it's too late. Sung Jin-Woo could also retire if he wanted to, but due to the immense power he holds and the responsibility on his shoulders, it seems unlikely. Can you imagine a hunter of Jin-Woo's level retiring at this point in Solo Leveling? Probably not.