Remember that first night in the hospital when the nurse made you wake your baby at 2am to feed it? Well that was probably just diamorphine in their system from the labour. It literally lasts one night.
Your baby will wake up at least twice in the night for the first few months. To be honest, apart from the obvious shock to the system, in hindsight the first few months are probably the easiest; you expect the 4am wake-up calls and sleepless nights.