[Canadian Man]

I wouldnt put too much thought into this topic in my opinion. Like you said there are so many varying answers that I don't think any way is correct.

My answer to your question is;
I use carbon all the time. I don't like to use it only for a few days then take it out because if it's in there all the time and you change it monthly usually your water will stay clear. When I tried to run it only a few days every month I found that my water would go crystal clear and then slowly go greenish then back to clear when the carbon was replaced.

I use seachem carbon(little sphere's ) and I use about 1.5 cups in my 90g tank with a 75g sump.

cheers