I don't wait any particular amount of time. If I make a quilt and want to repeat it again with new fabrics and new ideas and (fingers crossed here) new skills I jump in and go for it. After taking on a challenging quilt I would expect that you would have developed some new skills.
I have made a number of quilts a second time. Let's see.... HST's in the barn raising layout, one of the Mystery Train patterns from here on the board, Lori Holt's Cris-Crossed Stars are three I can recall immediately. Oh, log cabin of course. On the other hand there are some patterns that I have done as a challenge and shout hurrah when it is finished and move on. I conquered the challenge and don't have any desire to do another. Like KalamaQuilts said, "so many quilts and so little time."
BTW, Donna Jordan makes everything look easy and usually it is.
