Very similar to Sherie, my 3 all fell into a "groove" by themselves.

With Olivia, my first, I didn't really understand/appreciate it, but then when I had Charlie I realised that he too adopted a very similar groove, and so did Lexie.

All 3 of them kind of fell into a pattern of wake up, feed, play, feed, sleep. I couldn't/wouldn't "time it" as such with a clock, but by around 12 weeks the pattern was predictable.

Of course, as they grow, the pattern shifts a little in as much as they are awake and playing for longer, and sleeps vary depending on teeth & growth spurts etc, but the basic pattern remained the same.

HTH