If you don't make enough money when every single one of your portfolio companies exits for $50M, then you're doing it wrong.
Second: you don't /have/ to have a /personal/ board seat
Third: funds typically have multiple partners
If there is one lead and five follows in a series A, do you really think there are six new board seats created?
You would have made nearly twice as much (with virtually no risk) if you had bought a government bond with the money instead.
You're right about current yields, but they're also at all-time historical lows right now.