It's interesting to compare the following quotes from Aristotle and Seneca regarding the number of friends the wise man should have:
No one can have complete friendship for many people, just as no one can have an erotic passion for many at the same time; for [complete friendship, like erotic passion] is like an excess, and excess is naturally directed at a single individual. And just as it is difficult for many people to please the same person intensely at the same time, it is also difficult, presumably, for many to be good. [To find out whether someone is really good], one must both have experience of him and be on familiar terms with him, which is extremely difficult. If, however, the friendship is for utility or pleasure, it is possible for many people to please, for there are many people of the right sort, and the services take little time.
- Aristotle, Ethica Nicomachea, Book VIII, chap. 6 §2
I should like also to state to you one of the distinctions of Chrysippus, who declares that the wise man is in want of nothing, and yet needs many things. "On the other hand," he says, "nothing is needed by the fool, for he does not understand how to use anything, but he is in want of everything." The wise man needs hands, eyes, and many things that are necessary for his daily use; but he is in want of nothing. For want implies a necessity, and nothing is necessary to the wise man. Therefore, although he is self-sufficient, yet he has need of friends. He craves as many friends as possible, not, however, that he may live happily; for he will live happily even without friends. The Supreme Good calls for no practical aids from outside; it is developed at home, and arises entirely within itself. If the good seeks any portion of itself from without, it begins to be subject to the play of Fortune.
Of course, you could argue that "as many friends as possible" could easily mean exactly as many as Aristotle think is possible - but it seems tempting to hear Stoicism as being reluctant to commit as much to another person as Aristotle seems to encourage. Or to put all your eggs in one or a few baskets, if you will.