Traditionally, initiates have been required to wait at least one month after receiving the First Degree Reiki attunements before receiving the Second Degree attunements. In this tradition, a wait of one year is required prior to becoming a Reiki master, and then an apprenticeship of one year is required before receiving the attunement which allows a Reiki master to pass on attunements.
There are those who teach the first level of Reiki in two day workshops, and there are those who teach the first two levels in two day workshops. Then there are those masters who offer intensive Reiki workshops in which people are initiated into the first, second, third, and master levels in one weekend.
It is not the length of study which is important, but rather the needs and readiness of the initiate which must determine the length of study. Some people do need a lengthy time to assimilate all that Reiki is and all that Reiki means. Others do not. The Earth has undergone a great many changes since Mrs. Takata attuned the first American Reiki masters, and with the rapidity of change which is currently taking place, many people are able to receive and assimilate the Reiki attunements in a shorter period now. Arbitrarily established mandatory lengths of study are no longer necessary. The Higher Self of each individual understands exactly what the person can or cannot handle in a given time period. Reiki master teachers who offer Reiki in lengthy programs do not suffer for students any more than those who teach intensive programs. It is to be noted that lengthier programs generally cost quite a bit more than their shorter counterparts.
A slower study does not necessarily mean that the student will learn any more than the Reiki candidate in an accelerated program. Indeed, quite often techniques offered routinely in intensive programs as part of the regular curriculum are often offered only as separate courses by those who advocate lengthier periods of study. The ruling concept in intensive programs seems to be that the student of Reiki in such a program has ample time to practice what is presented during the class, and then has a lifetime to learn more. Given the abundance of books available on Reiki, this is not too far-fetched an idea. The student motivated to take Reiki training in an accelerated program will more than likely be motivated to do further reading in the area. The difference, then, seems to be more whether one wishes to pay for extensive practice, or to practice on her/his own after completion of the Reiki training.
None of this is to say that one method of training is better than the other. It just means that the choice should be left up to the individual Reiki candidate. Extended courses should be able to stand on their own merits, not supported by the fear-mongering of those who offer them. Similarly, intensive courses should stand on their own merits and those who offer them should not attempt to denigrate the lengthier courses. Each type of course has its own particular audience. Initiates from both types of courses are capable of being excellent practitioners.