Aei (G104) is an adverb of perpetual continuity — what is 'always' true or ongoing. In the NT it describes the constant wandering of unbelievers (Hebrews 3:10), the constant lying of Cretans (quoted by Paul in Titus 1:12), and significantly Paul's claim that he is always (aei) being given over to death for Jesus' sake.
Aei highlights the contrast between perpetual sinfulness and perpetual grace. Hebrews 3:10 quotes Psalm 95 — 'they always go astray in their heart.' Paul answers in 2 Corinthians 4:11 — 'we are always being given over to death.' The perpetual pattern of human wandering meets the perpetual pattern of divine sustaining.