"Much water makes up the sea. But extreme watchfulness and the Prayer of Jesus Christ, undistracted by thoughts, are the necessary basis for inner vigilance and unfathomable stillness of soul, for the deeps of secret and singular contemplation, for the humility that knows and assesses, for rectitude and love. This watchfulness and this Prayer must be intense, concentrated and unremitting." (Philokalia page 164)
St Hesychios here seems to be warning against half-heartedness when praying this prayer. It requires "vigilance" and concentration as well as "extreme watchfulness". The occasional repetition stands at odds with his advice. Not that praying it a few times a week is bad - its just not best.