The “purpose” of spiritual evolution is not the attainment of “spiritual perfection” - not in the sense of not having to evolve further, at any rate, since there is no such thing. We need to evolve in order to grow - but we can take rest breaks (hopefully well earned :) ) along the way. No, the “purpose” of evolution is, rather, to perfect our ability to learn, and thus grow.
If you want to read more, the definition is here.