Back when I regularly wrote white papers/explainers/etc. of various sorts (3K-4K words or so), I often felt a need to redo a piece that was 12-18 months old to fix a couple things that weren't correct any longer, shake any dust off, and so forth.
Invariably, half the thing ended up being rewritten to various degrees. It was still a lot easier than starting from a blank sheet of paper but, as soon as you rework something, you don't want to ignore all the sections that aren't quite fresh, want to bring in new facts and figures, bring in more recent examples, etc.
And, in reality, the extra time is probably justified because the act of opening up an older piece, republishing it, and all the associated background machinery makes it worth spending a bit more time.
Invariably, half the thing ended up being rewritten to various degrees. It was still a lot easier than starting from a blank sheet of paper but, as soon as you rework something, you don't want to ignore all the sections that aren't quite fresh, want to bring in new facts and figures, bring in more recent examples, etc.
And, in reality, the extra time is probably justified because the act of opening up an older piece, republishing it, and all the associated background machinery makes it worth spending a bit more time.