You asked: "can the human brain really tell a difference in that time span of thousands of seconds?". My answer is: I dunno. But, I do know, I believe I can tell the difference. I have seen the vids and have seen the results. The difference, if any, is, supposedly, too small for the human brain to notice. I always use 4Fg for prime because when I started this game an old timer mentor told me "you are supposed to". So I did and got in the habit. Now, I have several pounds of 4Fg on hand that will last me years. I use it because I prefer it and have it. That is part of playing this 'do yer own thang' game.