I don't think it will ever result in a permanent mute, because temp-mutes all expire after a year. And if you ever do get perm-muted from multiple temp-mutes, you can't* get muted anymore because you can't use the chat. Then the only thing that can happen is the current temp-mutes will expire.
I wouldn't worry about it. It would take a lot for it to accumulate enough to warrant a perm-mute, anyway.
*I've gotten a mute for spamming quickchat while muted. But nothing happens because I was already muted. But the offense did show up.
Interesting question, btw.