Love and worship are normally considered to be particularly beautiful when they are spontaneous. However, that doesn't necessarily mean that there is something wrong with scheduled worship. In this chapter, we find that David scheduled who would lead in worship and when they would do it during each year. And, his plan lasted all the way to the days of Jesus (compare Luke 1:5, 8 & 9 to 1st Chronicles 24:10).
There were 24 families who were assigned to govern the sacrifices in the temple, each for 2 weeks annually... 16 of them were descendants from Aaron's son Eleazar, and 8 of them were from Eleazar's brother, lthamar. Eleazar had been the oldest of Aaron's surviving sons, but lthamar was selected originally to be the high priest after Aaron. And, Eleazar's family got that honor back because of the failure of lthamar's descendant, Eli (see 1st Samuel 2:31 & 35).
There was distinct organization to the priestly ministry, even though it was an intensely spiritual undertaking. The easiest way to explain this concept is to consider married life. While spontaneity is a prized ingredient in the marriage relationship, planning is just as vital... if not more so. Being intentional; scheduling in time for one another is meaningful and productive. Arranging time "just for you" says a whole lot about how important one's spouse really is. In the same way, there is certainly nothing wrong with planning and organization in our religious devotion (1st Corinthians 14:40). While if we aren't careful we can schedule the Holy Spirit right out of our churches... He can just as easily help us to schedule Him right into our midst as well... if we will just let Him.