[Lucas89]

I would say when you can read kana your good to go with sentences.
I have been doing sentences the whole time, it doesn't matter when you start them but i think the earlier the better.

You don't have to go through the same "phase" order as Khatz did it, for example although i like the method, agree it works, and do it all the time, i didn't pay any attention to what order his says to do things in.

In the end if you think your ready to do sentences, then do them, same with all the other "phases"