Let me try again and explain what my concern is about these FriXion pens (and I do loooove to use them for jotting down this and that on paper):
I do not intend to freeze my quilts, and I don't intend to move to Alaska or Iceland and use my quilts outside.
But: At this point in time we do not know what the chemicals in the pens will do to our quilt in a few years. They may be perfectly ok, or they may destroy the fabric. At this point, we do not know.
We DO know that if FriXion pens are used on fabric, the chemicals will not wash out, whatever method of washing you use.
I do not know what exact chemicals are used in the FriXion pens, but they use 'thermoreactive dyes', and they always contain some or all of the following chemicals: Leuco dyes, spiralactones, fluorans, spiropyrans, and/or filgicides.
So, it's up to each of us. Personally, I will continue to use these pens on paper (what they were designed and developed for). For marking quilts I will use methods with a longer track records.