Final report. I replaced the Mylar with aluminum foil. It's got a lower WVTR (water vapor transmission rate) and conforms better for the seal. After 10 days (Erev Sukkot to this morning) being on a table the entire time, the rayon and tyvek wrapper worked phenomenally. Hadassim & aravot in great
The best method for keeping hadassim & aravot fresh for all of Sukkot is disputed. As I don't have enough fridge room and find damp paper toweling and foil primitive at best I have moved into the 21st century. 4 mil Mylar, Tyvek 10G, and 70gsm Rayon. Four days; still damp; vegetation is great shape.