Questions about discontinued pieces, sets, colors, or themes.
Sometimes pieces are discontinued. While it's safe to say that the red 4x2 brick will always remain, other non-basic pieces or colors may not be so lucky.
Whole themes can be abandoned as well. Fabuland, for instance, is no longer around.
And of course colors aren't safe either. Around 2004, dark grey was replaced by dark stone grey (also know as bley).