Tired blip

Zombified mummy today. The boys decided sleeping at night was for losers last night and other than about 30 mins if sleep stayed away crying, eating or needing a cuddle until 6:30am!! They then proceeded to sleep for 5 hours. I know it'll settle down but god I wish they would hurry up!! Currently waiting for them to wake up for their next feed and if they go back to sleep after it may try and have a cheeky bath. Can some tell me why if I make up their feeds in anticipation of them waking after 4 hours they stay asleep and it goes cold, yet if I don't make one up they wake up screaming and desperate to be fed and it's too hot for them! Sod's law I assume