Kṛṣṇa is sanātana, and His dealing with His devotees, that is also sanātana. And these are possible not here, but in the sanātana-dhāma. We cannot have sanātana dealings with Kṛṣṇa within this material world. Therefore Kṛṣṇa comes to canvass the conditioned soul that, "For eternal happiness, for eternal dealings, you come to Me in My eternal place." Yad gatvā na nivartante tad dhāma paramaṁ mama (BG 15.6).
Why not in this material world? No. The material world, the nature, is it is not permanent—it is temporary. Bhūtvā bhūtvā pralīyate (BG 8.19). Janmādy asya (SB 1.1.1). Janmādi. Everything here in this material world has a date of birth, and anything which has a date of birth must be a date of death also. That is the nature of this material world. So here we can practice what is sanātana-dharma, but actually sanātana-dharma is executed in the spiritual world.
So just like one is trained up to become apprentice in some business, and when he's trained up, then he's given the post, so we get this information from the gosvāmīs, sanātana-gosvāmīs, that those who are devotees, those who are perfected in the training of devotional service, they are first of all given birth in the universe where Kṛṣṇa is present.
Kṛṣṇa is always present, just like the sun is present always in the sky, but we can see the sun in some opportune moment. But sun is always there. When the sun is set, it is set in my vision, but sun is there.