Studies have shown that we retain movements in different ways, ex:
Gross motor skills are the easiest retained and applied under pressure than fine motor skills.
If you want to retain things quickly for short term, you would do lots of repetitions over a short period of time ( 1000 reps for every day for a week for example).
If you want to retain over the long term, you would do a moderate number of reps, daily, over a longer period ( 50 reps every day for 1 month as an example).
So, gross motor skills are easily trained with the short tem method BUT finer motor skills require the long term.
As for time/length of training sessions, all that depends on the intensity of the training.
You can train for hours if you are working low intensity BUT if you push yourself hard, an hour is great for a high level athlete.
I am, of course, referring to CONSTANT training with minimal variation in intensity ( NOT HIIT since that would lessen the time for half that at best).
Again, the more intense the less you can train.
Forms fall under the category of low to moderate intensity.
Psalms 144:1
Praise be my Lord my Rock,
He trains my hands for war, my fingers for battle !