its always better to be safe then sorry. Again it depends on the ultimate use of the quilt. If wallhanging and never washed then I don't.
However, I bought 7 coordinating pieces at the local big box store. They had a good coordinated group and the quilt is going to someone I know only casually. I used the pattern used as learning a new technique.....so with this said.
I washed it all and glad i did because there was considerable difference in the quality within the 7 pieces, a couple shrank badely while others didnt. And since there was a lot of bias edges Iam sure I did wash.
So ultimate use and then better to be safe than sorry about the results. If i don't wash then i at least spray and steam press or wet the piece and iron dry.