My LO used to go bed really well sleeping a good 10-12 hours.
He needs going to bed roughly same time as usual give or take 30 minutes,
He is going down 630ish and started waking around 11pm for like an hour or two and when I have work the following morning it is quiet tiring.
Sometimes goes till 3am and likewise same for an hour or two, sometimes he has a nap during the day sometimes not, but still the same at night.
Don't know if a phase or what, but been going in for couple months now xx 