What works here is if I plan to do boring stuff like housework that evening he doesn't wake when I sneak off and goes down for the night - so I am doing the washing up almost willing him to wake so I can leave it. If I plan on doing anything else slightly fun or interesting he is guaranteed to not want to go to bed until I do! So sorry not very practical advice but I would just keep trying and convince yourself you love the extra evening hours together and then he will probably start going to bed earlier just to be contrary.