Regarding your question about eternal spiritual and temporary spiritual, the temporary spiritual is the impersonal brahmajyoti. The impersonalists by severe austerities and penances arise to the Brahman effulgence. But it is only temporary. Eternally we cannot remain aloof. As living entities, we want pleasure in association; therefore we see in the material world where for sense gratification the karmis take so much responsibility. First of all they accept one wife. The more he enjoys the wife, the more he becomes implicated. So, this means that we must have pleasure even at the risk of gross implication. Therefore our Krishna Consciousness movement is that we want pleasure but without any implication. This is happening actually. All of our Krishna Consciousness students they are enjoying life without any implication.
Letter to Sridhara das, 19 August, 1974