One to two years is correct . . and it does depend mostly upon the priest. It is also correct that each “year” of RCIA corresponds to a typical school year, beginning in September and going until Easter Vigil, at least that is the way it happened at my parrish. I started the RCIA process November 2001, and because I did not receive a full year, continued the next year and was received into the Church Easter vigil 2003. However, my two oldest children, who had been baptised in the protestant church we attended before my conversion, were also received easter vigil 2003, with only one year of CCD and decision rested in the judgement of our priest.
Each situation is different, having all manner of circumstances that make it hard to say what is going to happen in each case. Normally, one to two years, but all at the discretion of the priest.
I will always value the time I spent in preparation, deeply longing to receive Our Lord in Holy Communion. While it seemed pure torture at the time, waiting produced tremendous growth in virtue. Also, my sons would not have been able to come with me had I been received after only a partial year in RCIA.
What is your reason for asking? Is this for yourself or for someone else?