Halflife under normal circumstances. Deepfreezing it is not the usual for DNA. Just like your meat and vegetables are still edible when you freeze them a year later and spoil in a matter of hours or days at higher temperatures.

http://rspb.royalsocietypublishing.org/content/early/2012/10...

So that's at 13.1 degrees, quote from the end of that paper:

"Our results indicate that short fragments of DNA could be present for a very long time; at –5°C, the model predicts a half-life of 158 000 years for a 30 bp mtDNA fragment in bone (table 1). Even rough estimates such as this imply that sequenceable bone DNA fragments may still be present more than 1 Myr after deposition in deep frozen environments. It therefore seems reasonable to suggest that future research may identify authentic DNA that is significantly older than the current record of approximately 450–800 kyr from Greenlandic ice cores".

So even if they don't have a thermal model where you plug in any temperature and it will give you the half life there is good evidence that lower temperatures significantly increase the chances of DNA remaining intact for much longer than the above-zero half life would suggest.

That is if completely unmaintained and under much worse conditions.

Bacteria in the permafrost have been found to have been repairing their DNA for almost half a million years. IIRC they aren't really active, they don't reproduce at all, only a very minimal level of metabolism is maintained to repair occuring damage in the cell.

The Worms could be similar. Being frozen, they merely shut down everything but the absolute minimum of metabolism, likely powered by minute temperature differences or incoming light from the outside or many of the other options, just enough to keep the DNA and cell intact, the worm itself would likely be considered dead in it's frozen state.

But they are waiting.

This depends only on system input energy statistics.

At low temperatures (the lower you go) and low radiation (the lower you go) there is not enough energy in the system to exceed activation energy and break down DNA (meaning statistically it's extremely unlikely (arbitrarily) for enough energy to enter the system in a short enough period of time to break down the structure) (there's always the minuscule chance that some wavefunction posits enough energy into the system of course).

DNA can be repaired. Decay of organic structures is mostly just breaking apart. This is much more reversible than reproducing radioactive elements from decay products.

Ideal conditions in very cold temperatures.

it depends on the moisture, salt, and temperature conditions. DNA kept in dry, cool conditions with the right salt concentrations is effectively stable (very very low base transversion and strand breakage rates).