There is no doubt that uttering HARI NAMA even once earns moksha.
Just as the greed and taste for wealth does not subside, the taste for bhakti and Nama does not subside. Any amount does not suffice.
Just as wealth accrued by a man is useful to the world and for future generations, a man's bhakti and the power of Nama gives strength to innumerable people
Please check these: Excerpts from a discourse by our Sri Sri Muralidhara Swamiji