As we know it is a sin (I believe mortal) if a religious or priest were to purposefully and willingly neglect praying one of the hours of the Divine Office. There may also be some illicit forms of praying it (I suppose if they changed the hymn or psalms without provision? or perhaps skipped a part.) I think my main question falls into the latter. If a religious superior of an order had decided to pray the Liturgy of the Hours in a certain way that was illicit, would have to be obedient even though that was the case?
But my main question is this, If a religious superior decided to combine two hours (excluding the Office of Readings) would that be licit? Let’s say the decided to combine Terce and sext (mid-morning and mid day prayer) or sext and non (Mid day and Mid afternoon)? a step beyond that, what If they decided to combine all 3 daytime prayers? My question is, would the superior or those under him be culpable of sin for following this practice?