When we profess that the Church is "one, holy catholic and apostolic", by apostolic we mean
—she was and remains built on "the foundation of the Apostles,"the witnesses chosen and sent on mission by Christ himself;
—with the help of the Spirit dwelling in her, the Church keeps and hands on the teaching, the "good deposit," the salutary words she has heard from the apostles;
—she continues to be taught, sanctified, and guided by the apostles until Christ’s return, through their successors in pastoral office: the college of bishops, "assisted by priests, in union with the successor of Peter, the Church’s supreme pastor" (Catechism n. 857)
But today's first reading picks up on a dimension mentioned in the first paragraph but easy to overlook, "witnesses chosen and sent on mission." One of the things that distinguished the apostoles from other ministers in the Church was the itenerate nature of their ministry. As we follow the journies of St. Paul in the Acts of the Apostles, we are reminded that as apostles they never settled down.
The apostles moved from city to city, as they established a community they appointed presbyters/bishops and then moved on. The presbyters/bishops (presbyteros/episkopos) would be the stable leaders of the community. Even today we struggle with finding the proper balance of the two values: stability and mission.
The presumption of the present Church is that a bishop once named Diocesan Bishop will remain until age 75 when he is warmly encouraged to submit his letter of resignation to the Pope. A priest once named Pastor is presumed to enjoy that same stability of office and is requested to submit his resignation at age 75 (c. 838). The norms of the universal church see stability of a diocese or parish as a particular value for the good of the bishops, priests and most of all the people.
In 1984 the U.S. Bishops were allowed to establish a different policy for the dioceses of our country. In the U.S. pastors may be appointed indefinitely or for a six year term which can be renewed. It stuck the balance between the two extremes of the irremovavable pastor of the old days and thinking that a pastor serves at the pleasure of the bishop.
As human beings we like stability. We like predictability. Unpredictable scares all of us. On the other hand, we must remember as a Church that we are always called to be apostolic, constantly missionary. And we should never forget that the word misson or missionary doesn't refer to going, it refers to being sent. I go on vacation. The Bishop sends me to my next mission.
For a parish the change of mission may come in the form of a change in the neighborhood around it. How many churches have died because they refused to embrace the new mission?
Paul and his companions never ceased to move on from one city to the other, from one mission to the other spreading the good news. We may pause for a brief time and settle down but God is always calling us to move, to change. Our pilgrimage, our apostolic journey does not end until we reach the end of this life.