Except that's just 40% of your blood (by volume) and it happens on a continuum, as every second new red blood cells are generated

white blood cells (~4% blood volume) live ~15 days

39% is protein, most of it albumin, which leaves the bloodstream at a rate of 5% per hour. It has a circulatory half-life of about 16–18 hours and a total half-life of about 12 to 19 days in a healthy young adult!

Your blood is mostly water and is constantly being filtered by your kidneys, with old water leaving and new water coming in!

The body is amazing!