Is this the quote by K.H. that you are referring to?
After the completion of the great cycle [there is] either a long Nirvana of Bliss (unconscious though it be in the, and according to, your crude conceptions); after which — life as a Dhyan Chohan for a whole Manvantara, or else "Avitchi Nirvana" and a Manvantara of misery and Horror as a —— you must not hear the word nor I — pronounce or write it. But "those" have nought to do with the mortals who pass through the seven spheres. The collective Karma of a future Planetary is as lovely as the collective Karma of a —— is terrible. Enough. I have said too much already.
He seems to be stating that after the Manvantara (Cosmic Day), there is a period of Nirvana—“cessation.” We refer to this as the Cosmic Night, the Pralaya, in which activity ceases. During this period, one may experience a period of bliss or a period of hell, Avitchi, according to K.H.