How can I tell the difference between joy bourne of karma that will expire and joy bourne of karma which has turned the irreversible wheel of the dharma?
Denizens of the heavenly planets enjoy more and live longer. They have made lots of good karma in their human form of life and became qualified to enjoy heavenly life. The joy of of Buddhas is eternal and unlimited. Buddhas enjoy their natural life that's found in enlightenment.
The best way to know this is by gaining experience from meditating.
The Deva Realm is one of the six realms of Saṃsāra, implying Devas are still subject to Karma. Simply put: what goes up, must come down. Existence in the Deva realm is temporal, and therefore the joy it brings is temporal, sensorial, and driven by the ego.
The Buddha and Boshisattva realms are not on the Samsara map, implying they are either not subject to Samsara or that Samsara is Nirvana (opinions on this will vary from lineage to lineage). The joy of this state is considered non-temporal and non-individual as it stems from compassion, is not induced by the senses, and is in essence non-dualistic.
Cosmologists today attribute approximately 5% of the cosmos to matter i.e. the material world of the planets and stars, approximately 35% of the cosmos to dark matter and the balance 60% or so, to dark energy. Scientists say that in the realm of dark matter light is reflected whilst in dark energy no reflection takes place. According to Buddhist cosmology, it is conceivable that the deva world (only the higher senses are present i.e. sight, sound, mind) represents the realm of dark matter and the brahma world (only the mind/cognition is present) represents the realm of dark energy. These three realms may be defined as samsara. It is conceivable that Enlightened beings living in the realm of Nirvana may be either in the ''higher frequency band' of dark energy or in a realm unknown to science.