From what I can gather, the Vedas and Upanishads and Hinduism in general state that punishment via hell or rebirth in a bad state of life, and Heaven or rebirth in a good state are always temporary as is all existence and everything other than God. Ditto for everything in between. Literally everything, without exception is temporary except God. Even if one were a being in heaven or a terrible asura for trillions of years, eventually that existence and the universe itself will cease and be reborn. The being in heaven may be reborn on Earth as a human, ditto for the asura.
So no heavenly being is ever safe from ending up as an asura or as a bug or something, and no asura is ever doomed to permanently be stuck as an asura and may end up as a human eventually who could reach God on a long enough timeline? Same for all levels of heavenly beings on through animals and bugs and down to asuras, with the only permanent abode being union with God after Moksha. And Moksha is available to all on a long enough timeline?
Is this correct? Could someone please provide some scriptural references (Vedas, Upanishads, etc.) that make it unambiguous that there is no such thing as someone who is forever reborn or permanently dwells in a certain domain, as all domains, beings, etc. are temporary?
If I am wrong, and certain beings do permanently dwell in one domain and/or some domains (other than God) are permanent, could someone provide these references as well?
If it is a mixed bag, and some texts say there are no permanent destinations, and others say there are, which is stated with the highest frequency?