Ancient history:
I made this cherry chocolate chip oatmeal cookie dough on 11/12/2006, one of three batches of cookies made in preparation for Thanksgiving 2006.  The other two cookie dough logs were actually used that year, while this one sank into obscurity at the bottom of my chest freezer.  A few weeks ago it resurfaced as I was reorganizing the chest freezer in preparation for a new influx of frozen meat.  These are the results of my forensic experiments.

Initial observations:
The cookie dough log was wrapped in plastic wrap, then covered in aluminum foil.  Thankfully, I'd thoroughly labeled and dated the log, so it was clear the thing was over four years old.  There was neither visible freezer burn (it would have appeared as dry, white patches on the surface of the dough) nor ice crystals.  It was clearly in pretty good shape, so I dragged it into HQ for proper examination.

Further studies:
Slicing into the frozen cookie dough log was challenging, but it came apart in chunks instead of clean slices because the dough was too dry. This condition was the same throughout the log, so I blame the recipe (or lack thereof - I usually make cookies by feel) and its overabundance of oats for an excessively dry dough.  I vaguely remember that the other cookie batches made at the same time were too heavy on the oats as well, and thus somewhat dry.

I baked the cookie chunks in a low 300F oven to give them more time to spread, but due to the firmness/dryness of the dough they retained most of their original shape.  They colored nicely in the oven, and had a good if slightly crumbly texture.  Testers at HQ were suspicious at first, but after an initial cautious sample ate them enthusiastically.  They'd be totally perfect dunked in milk.

Conclusion:
A fat-based cookie dough, properly packaged, can survive virtually unchanged for years in the freezer.  Make some now, and be prepared for the upcoming zombie apocalypse.