[Nobody's Confidant (OP)]

Do they circulate forever? Never dieing? Or do they wear out and eventually be made again?

Do I have just as many blood cells as when i was born? Or are there more now? Less?

Sorry, it's a lot of questions. Answering them all would be great, though.

[paul.fr]

Red blood cells generally "last" for, or have a life cycle of around 3 months. The individual cells are not (to my knowledge) "made again" but you do produce a few million of them every second.

An interseting fact is where their breakdown products end up. Ever wondered why your poo has a redish brown colour?

[Nobody's Confidant (OP)]

No.

[hamza]

An interseting fact is where their breakdown products end up. Ever wondered why your poo has a redish brown colour?

Well the colour of the poo comes from the bile pigments. The bile pigments are formed from the breakdown of haemoglobin, which is 95% part of the red blood cells.
                     And regarding the question posed by Rdn00b; well red blood cells have a life time of round about 4 months .. while the lifespan of whiteblood cells is of months or even years which depends on the body's need for the cell.