I wish there was an easy answer to this question but as usual it depends on a number of factors. I am working on several different crazy quilts at one time right now…go figure! Anyway, I have one crazy quilt (the one with color but neutral backgrounds) which I was only going to do about 5 blocks, but now I have 9. Sometimes the project just grows of its own accord or ideas that just pop up. First, I decided to take one of my favorite blocks and use it as an individual block with an elaborate border which would combine my two favorite types of quilting: free motion quilting and crazy quilting. Then I found a pair of white gloves that are absolutely beautiful with tiny pearl seed beads sewn on the top of the gloves. The gloves must go on something wonderful so I decided that this single block and the white gloves were meant to go together. Check out the picture of the work in progress! Anyway what decides how many blocks? Many factors such as how many things you wish to show off, how many blocks you decide to finish and whether you have a theme and how many blocks it takes to make that theme perfect! So the real answer is that it is a personal choice and only you know the real answer!