For a real insomniac, IMHO, everything is habit forming. I've been addicted to a sleep mask since moving into this house 2 yrs ago with windows facing the am sun. I can be in a coffin tonight and i still need the sleep mask or i'll struggle to fall asleep no matter how exhausted i am (i maybe i pass out, but if wake up in the middle of the nite i'll need the sleep-mask as a comfort to fall back). I've had month-long periods of being addicted to white noise in the past. And in the spring i often form an addiction to ear buds when the birds start chirping... and i'll require them even if the coffin is noise-proof.
At the same time, if i'm exhausted, i still have the ability to nap on a couch with no mask, no noise prevention stuff. I won't be long one since some noise will eventually wake me up, but it's just a different scenario entirely due to some weird context-specific habituation over time.
