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?
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.