my intuition is not to discount at all, i.e. my happiness in 50 years is worth exactly the same as my happiness in the present.

If you separate utility discount into uncertainty (which isn't actually a discount of a world state, it's weighting across world-states and should be separately calculated by any rational agent anyway) and time preference, it's pretty reasonable to have no utility discount rate.

It's also reasonable to discount a bit based on diffusion of identity. The thing that calls itself me next year is slightly less me than the thing that calls itself me next week. I do, in fact, care more about near-future me than about far-future me ,in the same way that I care a bit more about my brother than I do about a stranger in a faraway land. Somewhat counteracting this is that I expect further-future me to be smarter and more self aware, so his desires are probably better, in some sense. Depending on your theory of ego value, you can justify a relatively steep discount rate or a negative one.

Hyperbolic discounting is still irrational, as it's self-inconsistent.