Should I Cast On?

I kept waking up this morning with thoughts of a knit skirt, made out of my Alpaca With A Twist.  I kept thinking of if I would have enough yardage, what design to use, but haven't cast on.

The truth is that I am extremely tired of working on scarves and want to do something for me.  A skirt seems like a great idea, especially since I have yarn to do it with.

I suppose I will quell the urge by simply doing a gauge swatch. That usually helps me concentrate on getting my project done.