When it comes to moving your fingers, many short sessions are the way to go. The hand movements need to be automatic -- engaged without conscious thought -- and that takes time for connections in the brain to form. (Likely in the cerebellum, at a minimum, but I think the exact process for motor memory consolidation is not yet fully understood. There are some other complications, like what else one is practicing, but they probably are not worth worrying about in this context.)
"Cramming" might be an acceptable strategy to get through a test the next day, but is not a good strategy when you really want to know something long-term.
The underlying principle should be that one strives to practice something as often as possible, not for as long as possible.
Tom
