Less than weekly, but frequently
Also it should be noted that my almost two year old babbles constantly in a language known only to her, with a few english words sprinkled in. Entire statements, questions, arguments, and conclusions come out. We can tell by the inflection. But only 25% or so of it is decipherable.
Last week I noticed she learned the word "birthday".
My almost five year old speaks in english words, but even when I know the words, I still don't always know what she's talking about.