It's an old thread, so it's easy to miss.  No reasonable person would expect you to read all of the threads.

Stardock answered the "Preorder Cutoff Dates" thread...

While that's an uber vague answer, it is my understanding that they won't even have an alpha version ready for elite founders to try until at least January, so it might be okay to assume that we have until at least then.  It remains to be seen whether they will continue to offer "elite founder" option even after "alpha" versions have given way to beta versions, I have no clue.  I do not recall Stardock offering "elite" type deals before, though I was a pre-purchaser of War of Magic which wound up getting me Fallen Enchantress and Legendary Heroes for free.  I wonder if that accident played a part in inspiring Stardock to offer the Elite Founder deal.

Just another thing to note, it seems you don't get charged the whole hog at once either - my card got hit for a $2 charge when I ordered, but I haven't seen the other $97 yet.  Presume that it will probably be closer to the ship date/alpha date?