periodical

sequential

successive

periodic, recurrent, recurring, regular

alternate, alternating, cyclic (or cyclical), rhythmic (or rhythmical), seasonal, serial

aperiodic, erratic, fitful, irregular, occasional, spasmodic, sporadic, spotty, unsteady

continual, intermittent, recurrent, recurring

cyclic (or cyclical)

around-the-clock, hourly, round-the-clock

chronic, confirmed, inveterate

expected, usual