I am talking about a long run relation between two long run quantities, which either fluctuates in a certain band around equilibrium, or allows the economic equivalent of perpetual motion.

You seem to be predicting a diverging trend in that relation towards infinity, which is insane, as infinities tend to be.

I conclude from this you're misunderstanding the notion of "long term equilibrium" as stronger than it is in reality. Construct a model that simultaneously allows infinite divergence between securitized asset prices and their associated incomes, and disallows easy arbitrage, or we have nothing to talk about.

Every fool digs up that Keynes quote when his model is wrong.