The efficiency and speed of learning depends on a number of factors such as the difficulty of the learned material (how meaningful it is), its representation and physiological factors (motivation, health, stress, sleep, etc).
However in general, it's more efficient to get familiar with the learning material briefly, so you have time to process that new information subconsciously and come back to the material again to improve retention of that information in the human memory, rather than learn large amount of information at once.
This can be supported by the forgetting curve hypothesis which demonstrates the decline of memory retention in time:
Image source: Wikipedia
This shows that every time when you coming back to the same material, each time it increases strength and durability of that memory in the brain, so you are able to recall it for the longer period of time.
Definitely a spaced repetition could be more useful for improving learning and much more efficient in comparison of absorbing too much information at the same time (more than what is usually necessary) which makes your easily tired and exhausted, so the information is more impervious to being lost or forgotten.
See also: Spaced repetition, Forgetting curve, Forgetting, Mnemonic.