I think it's important to note that right now they are guaranteeing their "evergreen" model for... seven months. Let's open up the wayback machine and see how their claims have held up for seven months:
Scott Rouse, September 2008 wrote:The PDFs will be updated with errata around the time the Special edition core books come out.
The standard print core books will see it on their next reprint and that date depends on the rate of inventory movement.
OK, first of all the PDFs were never updated. The errata never got folded into books on reprinting, indeed most of the books never
got reprinted. But in any case, the second printings are line by line identical with the first.
Most telling of all, seven months later was April of 2009. What happened then?
Oh, right. The entire PDF operation was shut down.
Seven months after they promised the "year of the threes" they announced the Essentials line and canceled the DMG3. Seven months after they went to court claiming that "everything was core" they reclassified Adventurer's Vault and Open Grave, and almost everything else as a "supplement". Seven months is a
long time in 4e's marketing strategy, because they don't stick to
any plan for seven months.
What's odd is how actually not that long seven months is in real-people time. Six Harry Potter sequels took ten
years. 4e D&D has been thrashing around at a rate completely unheard of in the RPG industry - and practically unseen in
any industry. Even X-Men continuity is more stable than 4e D&D.
I can only assume that this has to do with lackluster sales performance and the short tales of the sales of items with poor word of mouth.
-Username17