So at 22 days and both leaves don't appear to have changed further for better or worse...
I'm thinking I'll remove one out and cut it to shape and in the process see if any dye appears to have been absorbed. Honestly, if it isn't the preservative, with this kind of longevity I'm tempted not to worry about preserving and simply cutting new leaves as needed. Thing grows like a weed and is related to a local invasive. If you ever want an indoor air purification plant that is virtually indestructible, it is the way to go though.