interesting topic......
heater packs are good for...cold climates. but dont put a heater pack in a shipment to FL. thats happened so often for me. i get a shipment and there is a heater pack in there, thats still warm.....in november in FL. bad news because its 80 degrees in the shade here in november. ive had water temps of near 90 on arival. maybe thats better than being cold for the first part of shipment. i dunno what the answer is, cheap self adjusting temp controll is not an option.
i would not mark the box with any special instructions....ie "fragile" "life" "etc." just pack it as good as possible in a plain box...ship overnight, and hope for the best. double/tripple bag, popcorn, styrofoam (reused maybe?) box, and temp controll if needed, but in my mind an well insulated package is mucho better than a heat pack or ice.
that and label the bags. the best shipments ive gotten have been labeled with the "type of light grown in...how far away from light source....salinity grown/kept in.....etc."
steve