Frank Senn makes an interesting comment on variety in the Western liturgy, suggesting that the confusing variety in the liturgy led to the development of a distinct – and much simpler – popular piety.
The most characteristic feature of popular devotions such as the rosary and the Way of the Cross is that they are repetitious and unvarying. The penchant for variety, which characterizes the religious professional (e.g., the monk or member of a religious order), does not excite the ordinary layperson. It may be that one of the features of Eastern Christian worship that has ensured its popular character is that, unlike Western liturgy, is not only highly ceremonial but almost unvarying throughout the church year. The consequence is that in the Eastern church, there was no rift between liturgical spirituality and popular piety such as occurred in the Western church during the Middle Ages.
– from Christian Liturgy: Catholic and Evangelical (Minneapolis: Fortress Press, 1997), pg. 239
I made my own comments about variety in the liturgy some while ago, wondering if seasonally-changing liturgical texts were unhelpful in forming the faith of Christians – Variable (or Vagarious?) Liturgical Texts.
The Lutheran Zephyr 
Our church uses about 3 or 4 liturgies from the ELW and one or two from WOV. This is decided by the worship committee together with the pastor. Then there are changes depending on who is the accompanist. For the musicians and choir, these changes are welcome. I often suspect that for the casual worshiper, they are confusing. From the choir area, I can see that there are lots of regular worshipers who never sing.
Then there is the issue of PAGE numbers and HYMN numbers in the books. Two weeks ago, an acquaintance I hadn’t seen in 25 years showed up in church. I could see that she was confused, so I actually left the choir and went and sat with her to help her with the book. This confusion was in spite of the worship leader announcing the page numbers we were using.
But still, the essence, the STORY, the WHY, we worship is there every week.
Now that I am no longer pastoring a parish, I’ve become an even bigger proponent of churches that offer different types of worship participation to their church communities each weekend. (2 or 3 worship services each with their own very different “style” but the same basic preached message)
Being creatures of habit, most people will attend at the same time each week and I think we church leaders tend to underestimate how much most people like to know what to expect at a church service. Consistently offering at least 2 types of worship allows people to choose one way of worship over another, and to reach out & invite friends & neighbors to church, knowing what to expect.
I would argue that at different points in our lives we need different ways of worship participation — for families with young children and for many aged people, or people experiencing stress and change in other aspects of their lives, for them, liturgical consistency may be the most powerful way to worship God with their whole hearts.
For others, that same “consistency” feels rote, empty, and b-o-r-i-n-g. They need and want to channel their energies into new, exuberant and/or
“edgy”, and experimental ways of worship. So let there be consistency in the inconsistency… at a fixed time for each. “There is a time for every matter under the heavens.”
Meanwhile, the spoken and proclaimed WORD of God provides the community-shaping essence and story each week (as Psanafterthought already said), no matter what the style of worship.