Join Date: Sep 2010
Location: In the shadows ...
You also must take into account that time within the Warp is not the same as the Materium. What is 1,000 years in the Warp, may only be 30 years in our time.
Time in 40k, as always, is hazy at best.
The chaos gods abandoned Horus most likely because they saw the can of whoop ass coming their way and wanted out of the way so as not to get fucked up!