Virat-rupa is temporary, for neophyte understanding...

Verse 1.3.3: Krishna is actually one without a second. This material world, Sankarshan maintains all the planets bearing it on His head.

The Lord's universal form is actually temporary. Once the mahat-tattva expands, then the universal from becomes manifest. When it goes back into pradhan state, the universal form becomes unmanifest. So basically Krishna and other incarnations are eternal, always existing in the spiritual planets, but the universal form is not. Krishna has nothing to do with the material world, He is always in the spiritual worlds.

First point to remember: We hear the names of Narayana and Vishnu more in the material world than Krishna, why. This is because Narayana is the incarnation in qualitative mode of goodness, is in contact with the material world for its creation, maintenance and destruction. Hence Narayana is more heard in this world. Whereas Krishna is always in the spiritual world, but just to take back conditioned living entities back to godhead, Krishna Himself appears once in the day of Brahma.

Second point: Unlike other forms of Krishna, the universal form is temporary.