The standard academic progression remains bachelor's—master's—(research) doctorate. Most standard "academic" programs are based on the four-year bachelor's degree, most often Bachelor of Arts (B.A.) or Bachelor of Science (B.S.), a one- or two-year master's degree (most often Master of Arts (M.A.) or Master of Science (M.S.); either of these programs might be as long as three years in length) and a further two to five years of coursework and research, culminating in "comprehensive" examinations in one or more fields, plus perhaps some teaching experience and then the writing of a dissertation for the doctorate, for a total of ten or more years from starting the bachelor's degree (which is usually begun around age 18) to the awarding of the doctorate. This timetable is only approximate, however, as students in accelerated programs can sometimes earn a bachelor's degree in three years or, on the other hand, a particular dissertation project might take four or more years to complete. In addition, a graduate may wait an indeterminate time between degrees before candidacy in the next level or even an additional degree at a level already completed. Therefore, there is no time-limit on the accumulation of academic degrees.