Hello,
I have an Infiniti G35 2004 with ~200k on it. Recently I have been having problems where when I shift to 5th gear (at 40mph or so) rpms jump from below 2k to close to 3k. So I decided to do a tranny fluid drain/fill since I haven't done that in a while.

I did the 1st one, about 3 quarts came out and tranny fluid was very dark brown. I am trying to do 2nd and 3rd drain/fill but I was wondering when should I do those? So I can have almost new tranny fluid

 

I have a dim recollection that folks have said something like 1,000 miles, but it's very dim. Hopefully you'll get some other votes to help you decide...