A couple of years ago I learned a kind of general pattern about cadences and took it for granted. the idea was that a cadence goes from weak beat to strong beat. It seemed that the first chord was either the same length or shorter than the second chord. It made sense since the cadence ends or pauses a phrase, and the final chord tells you where you have arrived.

I was working on a theory exercise harmonizing a melody, and it seemed that the middle (imperfect) cadence finishing the first phrase was coming out backward from this. It was 4/4 time, there was a for the next phrase in m. 4, so the cadence finished on beat 3. You'd have ii-V or IV-V, with ii starting on the strong beat 1 and V starting on beat 2 or beat 3. Having it start on beat 2 would mean the weak beat, and having it start on beat 3 would mean the stronger beat but it would be shorter. So this is backward from what I learned.

If there is a cadence like that, might it be that an imperfect cadence in the middle doesn't always fall that way?

By the way, I'm never sure if this kind of question belongs here or in the ABF. If someone thinks it's in the wrong place please let me know. Thx.

Forget the rule. Lots of cadences do that. Plenty more don't.