I'm not yet a versed expert in aging, although I am approaching such a state at what seems to be a mercilessly accelerating velocity. So, by all accounts, take the following with as many grains of salt as you find necessary in order to make it palatable: Age does not simply contribute to cynicism. Yes, you do continue to lose whatever rosy tint remains over your view of the world. But as everything outside becomes uglier, you eventually reach a point of reversal.
This assumes you have some sort of thing analogous to a soul, of course. But, assuming that, you do eventually come to the realization that the only possible rational response to the dreck and slime festering around you is to counterbalance it. Once you reach this point, you do continue to become more and more cynical - but this increasing cynicism in thought only feeds an ever-growing idealism in action. You become just as tired of complaining about things as you do of the things themselves. You realize all your moaning and tooth-gnashing has never convinced a single human being in a way that leads to any sort of improvement. Even those reveling in filth (e.g., hipsters) do this, this whining, even if regarding issues different than the ones you have become so accustomed to decrying.
So you stop. You stop bitching. You even try to not think too much about the things that bother you. But whereas you may have once done this because you were disturbed by the destination to which such roads could take you, you now avoid them because you are fully aware of them. You do not ignore them; you acknowledge them. You have become familiar. In some way, you embrace them. And in so doing, you have reached the point where dwelling on them does nothing but hinder your response. You know what your response must be, and instead of thinking about the problems, you think only of your own actions.
Anyway, that's my horrendously verbose response to that three-word conceptual equation. The "Cynicism = age + number of humans interacted with" question. Again, salt to taste. I am not old just yet, so who knows whether I will change in the future. I have many times already.
By the way, I don't think number of humans with which you have interacted affects your cynicism at all. The man who reaches death having had only one friend his whole life, will feel no less fulfilled than he who had many. If anything, I would wager he feels even more fulfilled. I see no reason why this would not also be true on the opposite end of the spectrum.