from the time they were born until probably the time my nephew graduated, but I can't think of a single thing either of them said that became common language in our house...except my nephew couldn't pronounce "piano" and instead called it a "pie-no-no".
OTOH, there's several things I remember my sister's kids saying, even though we only saw them maybe once a year, around the 4th of July (my mom's brother and wife always hosted a big shindig on the 4th). My nephew learned the word "aggravated" at a very early age (and used it correctly!) but couldn't pronounce it correctly, so he said "aggra-bated". My niece didn't adorably mispronounce words as she uttered memorable phrases. My favorite was probably during a squirt gun fight with her brother. She got wet, got mad, got her hands on a Super Soaker and drenched her brother, all while yelling "taste my wrath!". She was maybe 5 at the time.
