The book “Rite of Christian Initaition of Adults” gives some flexibility for such cases.
“76 The duration of the catechumenate will depend on the grace of God and on various circumstances, such as the programme of instruction for the catechumenate, the number of catechists, deacons, and priests, the cooperation of the individual catechumens, the means necessary for them to come to the site of the catechumenate and spend time there, the help of the local community. Nothing, therefore, can be settled a priori.
The time spent in the catechumenate should be long enough — several years if necessary — for the conversion and faith of the catechumens to become strong. By their formation in the entire Christian life and a sufficiently prolonged probation the catechumens are properly initiated into the mysteries of salvation and the practise of an evangelical way of life. By means of sacred rites celebrated at successive times they are led into the life of faith, worship, and charity belonging to the people of God.
77 **It is the responsibility of the bishop to fix the duration and to direct the programme of the catechumenate. **The conference of bishops, after considering the conditions of its people and region, may also wish to provide specific guidelines. At the discretion of the bishop, on the basis of the spiritual preparation of the candidate, the period of the catechumenate may in particular cases be shortened (see nos. 307, 308-311); in altogether extraordinary cases the catechumenate may be completed all at once (see nos. 308, 312-345).”
“2 CHRISTIAN INITIATION OF ADULTS IN EXCEPTIONAL CIRCUMSTANCES …
307 Exceptional circumstances may arise in which the local bishop, in individual cases, can allow the use of a form of Christian initiation that is simpler than the usual, complete rite (see no. 34,4). The bishop may permit this simpler form to consist in the abbreviated form of the rite (nos. 316-345) that is carried out in one celebration. Or he may permit an expansion of this abbreviated rite, so that there are celebrations not only of the sacraments of initiation but also of one or more of the rites belonging to the period of the catechumenate and to the period of purification and enlightenment (see nos. 308-311). The extraordinary circumstances in question are either events that prevent the candidate from completing all the steps of the catechumenate or a depth of Christian conversion and a degree of religious maturity that lead the local bishop to decide that the candidate may receive baptism without delay.
EXPANDED FORM
308 Extraordinary circumstances, for example, sickness, old age, change of residence, long absence for travel, may sometimes either prevent a candidate from celebrating the rite of acceptance that leads to the period of the catechumenate or, having begun the catechumenate, from completing it by participation in all the rites belonging to the period. Yet merely to use the abbreviated form of the rite given in nos. 316-345 could mean a spiritual loss for the candidate, who would be deprived of the benefits of a longer preparation for the sacraments of initiation. It is therefore important that, with the bishop’s permission, an expanded form of initiation be developed by the incorporation of elements from the complete rite for the Christian initiation of adults.
309 Through such an expansion of the abbreviated rite a new candidate can reach the same level as those who are already advanced in the catechumenate, since some of the earlier elements from the full rite can be added, for example, the rite of acceptance into the order of catechumens (nos. 48-74) or the minor exorcisms (no. 94) and blessings (no. 97) from the period of the catechumenate. The expansion also makes it possible for a candidate who had begun the catechumenate with others, but was forced to interrupt it, to complete the catechumenate alone by celebrating, in addition to the sacraments of initiation (see nos. 198-210), elements from the full rite, for example, the rite of election (see nos. 105-115) and rites belonging to the period of purification and enlightenment (see nos. 128-136).”
The above numbers are from the RCIA book used in Australia and England. The USA edition also has 76 as 76, but n. 307 above is n. 331 in the USA editon. (The Rites Volume One, Liturgical Press, 1990, ISBN: 0-8146-6015-0, page 214).