In the past, the Liturgy Office has received questions about the frequency in which Eucharistic hosts reserved in the tabernacle should be renewed. As most Catholics are aware, parishes reserve the Eucharist for a number of reasons:
The primary and original cause for reservation of the eucharist outside Mass is the administration of viaticum. The secondary reasons are the giving of communion and the adoration of our Lord Jesus Christ who is present in the sacrament. The reservation of the sacrament for the sick led to the praiseworthy practice of adoring this heavenly food in the churches. This cult of adoration rests upon an authentic and solid basis, especially because faith in the real presence of the Lord leads naturally to external, public expression of that faith (H oly Communion and Worship of the Eucharist Outside Mass, 5).
Canon law notes that “Consecrated hosts, in a quantity sufficient for the needs of the faithful, are to be kept in a pyx or ciborium [within the tabernacle], and are to be renewed frequently, the older hosts having been duly consumed” (c. 939). Renewing hosts regularly prevents the “danger of corruption” of the sacred species (c. 924 §2).
While there is no specific law which mandates the frequency with which Eucharistic hosts reserved in the tabernacle should be renewed, a commonly-accepted norm is that this should take place at least twice a month. This rule is based on the canonical principle that, “In sacred places where the Most Holy Eucharist is reserved, there must always be someone responsible for it and, insofar as possible, a priest is to celebrate Mass there at least twice a month” (c. 934§2).
Hosts that are more than two weeks old should be distributed as Communion to the faithful, especially to the sick who are unable to attend Mass. This rule applies to larger hosts as well, and care must be taken to regularly change hosts which are stored in lunettes and used for Eucharistic exposition.