For my professorial  readers (or otherwise readers with PI status):

How long does it take you to write, from scratch, a single-investigator grant proposal that will undergo peer review?

For physical scientists and many others, I am talking about a standard NSF 15-pager or similar. For biomedical folks, that would be an NIH R01 (however long it is).
I am assuming we are talking about a new proposal (not a resubmission), and I am also assuming that you don’t just drop everything and disappear into a cave to write, but rather continue to tend to other normal academic duties, like teaching or service.