7 week baby STTN

I've a 7 week baby and past 3 days he hasn't been waking up for his night feed. We tried to dream feed him but he won't be able to finish his milk. Is it okay for 7 week old who is gaining weight healthily to start STTN? How do you decide what time is the last feed before STTN? Or just ensure a maximum of 5 to 6 hours window?