The csf is continuously produced how often is it replaced

About 6 to 8 hours

Explanation:

The CSF is continually produced, and all of it is replaced every six to eight hours. The fluid is eventually absorbed into the veins; it leaves the cerebrospinal spaces in a variety of locations, including spaces around the spinal roots and the cranial nerves

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.