Usually 2 or 3. One is being machine pieced. One is being handquilted and the 3rd is a hand pieced 3/4" hexagon quilt that will be an ongoing project for years.
Sometimes, if I'm in the mood to cut, I will start another.
I do this because some days I just want to sit and do hand work, other days I'm in the mood to cut or machine piece. Always have something I can work on no matter what mood I'm in.