You do not say, but it is implied that you are referring to a single-string sequence of notes (else the quick answer is that if you are playing three different strings as in an arpeggio, use a-m-i). If so, the usual practice is to alternate two fingers - i-m most likely. Single-string i-m alternation is not much trouble up to say 600 strokes/minute, i.e. doing 4 notes per click at 150 clicks/min, i.e. 16th notes at 150bpm, assuming the beats correspond to quarter notes.
It is up to you if you want to try learning a-m-i alternation as well. I find it is a very different beast than learning quick i-m alternation. This is because the usual-for-me hand position setup (a bit angled towards the i finger) for i-m does not work well when you add the "a" finger which is shorter than the "m" finger but is on the "longer" side of it. So I find it is a different technique to master altogether.
1982 Anselmo Solar Gonzalez