Re: "Black Box" information retention?

>>> obd0 = zero
>>> obd1 = 30 secs

> Having typed the above, I remember now that I read once (not online)
that
> the black box actually holds more like a minute to five minutes of
engine-
> running time.
>
> The automakers are interested only in the events immediately prior to,
> and during, a collision or mechanical failure.\

Well again, the question comes forth...how far back is the information
about 
a crash retrievable?

If I wanted to access crash information from a day in the summer...would
it 
still be there?

Does it hold that information indefinitely...until the next crash? 
...until 
you drive it again? ??

Thanks for your help!