Multi level asociations

I may be wrong but as far as I know you just gotta keep cascading down
that way.
But DO keep in mind to make only those associations that are
absolutely necessary. For eg., if you're gonna display all countries
in a planet only at one place, and if you are not gonna build logic
around the planet has_many countries, through continents association,
then you could still get all countries in a planet by doing
planet.continents.countries without has_many :countries, :through
=> :continents.
Then again, Im not sure if you save anything by doing that.