What about limited time events? Should they be considered "errors" or some such? Because these are common tactics employed by mobile games. Ad has been noted, we also have precedent such as Destiny and LoL.
We also have another precedent, which I can advocate for more effectively, which is D&D.
This profile is based largely on a long deleted web enhancement for the game originally published by Wizards of the Coast back in 2003-ish. The article got completely deleted by the change of editions in 2008, from 3e to 4e.
Though, it is to be noted, WotC themselves provided archives of these articles for a couple of years (2009 fully til they were deleted again sometime in 2013). These has since been deleted also, though large amount of content from said archives are still recognized in the editions since (the character Meepo in itself appeared once more in 5e). So it follows our guidelines that, as long as the information is still recognized and not contradicted, they should be fine to use.