A court for the crime of explaining his ideas, for instance, sentenced Socrates, to death.
However, Victor Hugo said that if he were writing for his time only, he would have broken his pen and thrown it away or something like that. As so it seems that, in order for a philosopher to be relevant for the future as well as the present, he must take into account all of the objections to his philosophy which can be anticipated at the present time. Since we are not omnipotent, that's the best we can do. And it seems to me that the most frequent objections to modern and pre-modern philosophers come from the incompatibility of their philosophies with what is considered to be established scientific thought. For instance, Plato's theory of forms does not, to me, seem to jibe with modern physics and cosmology. And although I can only vaguely glimpse the psychology, which underlies Kant, it seems to be highly questionable. In my view, application of Kant's epistemology and metaphysics could never produce an artificial intelligence capable of passing a Turing test.
And so, it seems to me, the best way that a philosopher can keep from being dated. Not in the romantic sense; many seem to have not problem with that is to be aware of scientific knowledge, and integrated it into philosophy. Of course, this necessities an independent evaluation of the merits and draw backs of a given scientific idea, which necessities, in turn, a thorough knowledge of that theory.
After all, physics can give us insights into metaphysics, since both seek different ways to do the same thing. Psychology, sociology, anthropology, and archeology can give us insight into epistemology; various "soft" sciences dealing with comparative cultures can provide food of thought in ethics, and so on. History is, of course necessary to any understanding of philosophy: how it came about, what people did with it.
