I'd be a little sceptical about the claimed half-life. DNA is very fragile; the reason that the mutation rates are quite low in living DNA is the constantly-operating repair machinery, which can often fix both the point mutations and structural damage (such as strand breaks). As the last resort, a living cell unable to repair its DNA will self-destruct - and its functions will hopefully be taken over by other, similar cells.
Over time, non-living DNA tends to become a soup of short fragments. It is still possible to decipher at least some of the information thanks to the huge redundancy of the genome in your average multi-celled organism - but the computational effort needed to align the fragment is huge.
Personally, I am not holding my breath.