Aristotle, Nicomachean Ethics
H. Rackham, Ed.

in the event of the parties themselves changing, for if no longer pleasant or useful to each other, they cease to love each other. And utility is not a permanent quality; it differs at different times. Hence when the motive of the friendship has passed away, the friendship itself is dissolved, having existed merely as a means to that end. 3. [4]

Friendships of Utility seem to occur most frequently between the old, as in old age men do not pursue pleasure but profit; and between those persons in the prime of life and young people whose object in life is gain. Friends of this kind do not indeed frequent each other's company much, for in some cases they are not even pleasing to each other, and therefore have no use for friendly intercourse unless they are mutually profitable; since their pleasure in each other goes no further than their expectations of advantage.

With these friendships are classed family ties of hospitality with foreigners. 3. [5]

With the young on the other hand the motive of friendship appears to be pleasure, since the young guide their lives by emotion, and for the most part pursue what is pleasant to themselves, and the object of the moment. And the things that please them change as their age alters; hence they both form friendships and drop them quickly, since their affections alter with what gives them pleasure,