Old geezer angles: There's a long and winding road between "they followed your advice right away" and "giving them advice had no effect". Your advice, or some of it, could become their Plan B. Or something that they try a time or few in the future. Or something they pass on to a third person. Or a memory of your own preferences. Or part of how they start behaving when they're in a different situation, or getting up toward your age. Or an anecdote when they're speaking at your memorial.

And the tone and perspective of your advice counts for at least as much as the advice itself.

ADDED: How you react to people following, or not following, your advice is part of that "tone and perspective" stuff.