Last minute panic is good, but I prefer 3 am bouts of manic insomnia. You get your best prep done when your brain refuses to sleep but is too tired to filter out ideas you might think are too out there or just bad when in a more lucid state. They're all just ideas, and your brain just keeps chucking them at the wall until something sticks.

-ps: no this isn't healthy, but we all have our own ways of entering that creative flow state.