Contemplation requires serious effort.
It is not enough to have a particular idea about a matter, or a general thought or understanding of the topic.
Rather, a person must delve into it, in order to continuously try to expand his capacity to comprehend, to enter into its inner being in order to understand it to the best of his ability – the whole, as well as its component parts – in order to instill the abstract image in his mind as clearly and concretely as possible.
This requires a great deal of work.
Just as there is a limit to a person’s capacity for intellectual attainment, so too there is a limit to the time each person is able to do so.
There is no set expectation for each one.
Rather, what he can accomplish depends on the amount of time that he is able to devote to the task.
After all, these are not topics that one can exhaust within a set amount of time.
Rather, they are topics that a person can delve into more and more, spending more and more time on them.
They never end.
As time goes by, new aspects emerge for him to consider.
The deeper he goes, the more depth he discovers.
Rabbi Adin Steinsaltz