What is the best practice for writing large documents?

As of now I have tried two ways of writing a large document (over 100 pages), one is to have everything (even the bibliography) in one single .tex file, and the other is to split the document into smaller files, for example, by chapters.

Each ways have their merit but neither is perfect

• Using one single file is clunky.
• While multi-file has more clarity, but it is inconvenient for one reason: say I changed the key for a reference item, I have to go over all the sub-files and search for possible occurrences of that key. Whereas if I had one file, I only have to search once and click "replace all".

Is there a better practice for writing a large document? Thank you in advance!