This sounds different than how songs are used in our church. We learn a new feature piece (anthem) for each Sunday, and we usually start practicing it 2-3 weeks before the performance. I have been singing full time with the church choir for 4.5 years now, and I don't see more than the occasional "re-run" in terms of singing the same anthem a second time. When the choir is preparing for one of the major concerts (Christmas and Easter), we tend to sing easier anthems on the Sundays leading up the the concert, so we can spend more time preparing the concert pieces.
In our church we sing 3 different hymns with the congregation each Sunday, and each service features at least one feature piece (the anthem), which is usually sung by the adult choir, but sometimes is sung by one of the children's choirs or by a group of church teenagers (led by the music director) who play religious songs in a pop/rock style.
With two services on Sunday, there are multiple anthem slots to fill each week. During the summer, there is a less formal musical agenda, including some quartet and solo performances by members of our choir, and it is during the summer months when I have played the anthem song on the sax, joined by the music director on piano (he is an excellent jazz accompanist, so this is a real treat for me).