Know your limits and know when you're beginning to spread yourself too thin. I have zero information regarding what type of story you're talking about, or if the inclusion of multiple supporting characters are even necessary, but I wouldn't consider this an ailment. It sounds like you have a healthy addiction to expanding a story and giving it life by introducing multiple characters, and that's only a bad thing if you lose sight of the main objective of your story in favor of going down an endless side quest. Geralt might have time to clear out a monster nest or clear a contract on a Fiend, but the main goal is still finding Ciri.
The question of "How many characters would you consider is too many for a plot?" depends on their purpose. Are you adding characters to join the party and form a group on a long term quest? Or are you talking about lending a name or identity to a traveling merchant? Harry befriended Ron and Hermione on the way to Hogwarts and over the course of the school year, but it was a man named Ollivander who sold Harry his wand in the first place. All these characters are necessary for the plot but only Ron and Hermione were necessary in the long term. Once Ollivander sold Harry his wand, and once Harry left Diagon Alley, Ollivander's part in the story was over.
The introduction of new characters isn't annoying unless they overstay their welcome. Always let there be a reason for these new characters to appear at any point in the story, whether it's as simple as a town crier providing information to a passing Witcher in need of work, or being an old love interest who is currently trying to help mages escape witch hunters, all while being a mage herself. Whether the role is big or small, let there be a reason we're reading this interaction play out, and don't overextend their role if they no longer serve any use to the main story.
Your support makes Blue Moon possible (Patreon)
