The boy leaves behind the strict, measured world of adults where everything is dictated by hours and minutes. He enters a place where time is defined by experience and freedom, not schedules.
The phrase “for ever” suggests a complete and permanent escape - he is fully immersing himself in the childlike, imaginative world, where life is about doing, feeling, and enjoying, rather than obeying the clock. it also reflects innocence and the timelessness of childhood.