Is it a waste of time to spend three months surveying five parts of the Qur’an, while I am still in the fourth part?

If the intended meaning of "sabr" (deliberation/exploration) is contemplation of Allah's verses for admonition and adherence to their commands and prohibitions, then it is legally مطلوب (desirable/required), provided it is done with an understanding derived from the imams of tafsir (definition) (exegesis). However, if the intention is to extract understandings and rulings without referring to the books of tafsir and the understanding of the reputable imams, then it is forbidden and considered speaking about the Book of Allah without knowledge.