Great job ... and thanks for the site link!
I'm like you ... I take it more seriously if I am doing something for "real" instead of a practice sandwich.
Here's another idea that I did ... I chose a front and backing fabric and make purpose sandwiches (not practice sandwiches). On each I practice whatever I want and then they will be joined together as a QAYG quilt. Sometimes it's trying out a new FMQ design or idea I have. Sometimes it's to get my machine set up and to get myself warmed up, before I go at whatever I am doing. I did 12-1/2" unfinished blocks, though the next time they will be larger (16-18"?) as it gives a larger work space. Of course, not as large as a full quilt, but definitely closer in a simulation.