As a matter of usual practice
customarily, habitually, punctually, systematically, unchangingly, right along, as a rule, routinely, usually, commonly, as a matter of course, tirelessly, conventionally, ordinarily, repeatedly, recurrently, frequently, orthodoxly, faithfully, religiously, mechanically, automatically, without once missing.
With little or no deviation
normally, periodically, evenly, methodically, exactly, monotonously, rhythmically, steadily, unbrokenly, typically, continually, like clockwork, mechanically, cyclically, seasonally, day in and day out, constantly, always, ceaselessly, time and time again, day after day, invariably, redundantly, hourly, incessantly, daily, perpetually, over and over again, weekly, monthly, annually, quarterly, diurnally, at regular intervals.
Antonyms irregularly*, unevenly, erratically.