There are of course exceptions depending on the topic...though for the most part why limit ourselves to only the most recent and active topics?
The way I see it, if someone comes to a topic that hasn't been touched for three solid years, why should that deter them from contributing to it? Maybe they have something that would be really beneficial to add...but if they have some pre-conceived limitation in mind then nothing is shared and no one else benefits from it in the present or future. Just my two cents worth:)
An example of an exception could be a topic about some new product that is "coming out in the next year" when it's actually been out for the last two or something.
Of course...in the event I've somehow missed somewhere on this site where they say not to kick-start old topics then by all means, let me know