My ds who is now 12 *used* to non-stop talk when he was around 4-6 years old and it was so insane trying to keep up with all of it - he wasn't just chatty, he was talking *deep* deep thoughts, complicated questions etc. That was long enough ago I don't remember how I survived the insanity lol, but fwiw in his case, he quieted down eventually and now does the excited-talking every now and then but not nearly as much as before. He still likes to have someone close by all the time though, but now he's much quieter. I think maybe part of it with him is that he got a little older he could do more on his own to focus his interests and look for answers to his never-ending questions (read, look for info online, that sort of thing). Now when he's uber-excited talking, it's usually to tell me about something he's figured out, not to ask the questions.
HOWEVER.... that doesn't mean it's quiet at my house! My dd9 is also very extroverted and starting the non-stop talking about one year ago, and for her, I'm not sure it's a phase - I think it might just be her. I'm an extremely extroverted person and also like to talk, but she's pushed the envelope so far it's literally driven my nuts at times! She'll be chit-chatting away about nothing and I or one of the other kids will just be at our wits end, so I'll tell her she needs to stop talking for 5 minutes or whatever and she'll happily say ok, and then launch right into talking about some other subject and not realize she's talking!
Like the others have mentioned, she doesn't really do this during school (except at recess with her friends). She's always been an extremely high-energy kid so one thing that helps is to involve her in sports that take a lot of energy - she loves to rock climb, ski, ride bikes, things like that. She's recently been interested in ballet, and when she's dancing she's incredibly focused. Sooooo... I can send her off into another room to practice her dance and that gives me a few minutes of quiet
Another thing that works well for her, since she is so very extroverted, is to simply have a ton of playdates. Her best friends are extremely chatty to, but it's easier for me to tolerate the intense chattiness if it's the girls chatting up each other in a different room than me being the sole focus of her need to talk.
One other note - she had some struggles in school early on (due to a vision challenge that we were unaware of), plus as I mentioned, she's a high-energy usually in-motion kid. Many of us (drs and me included) thought she was ADHD when she was younger, but she went through thorough evals and is most definitely not ADHD, just a highly energetic kid!
Best wishes,
polarbear
