Akshara means one who does not decay with time. Time is controlled by the Supreme Lord and hence there is no decay of the Lord.
ekas tvam ātmā puruṣaḥ purāṇaḥ satyaḥ svayaḿ-jyotir ananta ādyaḥ
nityo ‘kṣaro ‘jasra-sukho nirañjanaḥ pūrṇādvayo mukta upādhito ‘mṛtaḥ (SB 10.14.23)
You are the one Supreme Soul, the primeval Supreme Personality, the Absolute Truth — self-manifested, endless and beginningless. You are eternal and infallible, perfect and complete, without any rival and free from all material designations. Your happiness can never be obstructed, nor have You any connection with material contamination. Indeed, You are the indestructible nectar of immortality.
With this Holy name we complete Shloka 2. Chant the Holy name praying that our devotion to Him never diminishes.
Nama 17 – VishnuSahasranama