RegEx could be a little bit slow (by its nature), but you may try this too:
Search & Replace
Find: (.{4689}\s)
Replace: \1\n
Explanation:
Find one piece of any sign (char, digit, sign) by the dot, and that at least 4689 times.
The \s ensures that we break at a whitespace only.
I don’t know why this works, as the normal syntax would be {4689, } ( {m,n}, so 4689 at least, but more possible till a whitespace is found)
But it works fine.
Then we replace by what was matched into (…) back reference group and insert an line break. (\n is enough, even on DOS/Windows, see Help)
HTH?