Is there a temperature range at the departure, destination and major hub that the fish are likely to go through concern (think fed x and Atlanta)? My thought goes even with insulation and heat packs that very cold weather or very hot weather can play havoc with the water temperature and therefore the health of the discus. A long trip on a not well insulated delivery truck, warehouse, tarmac, delivery truck etc. in very cold or very hot weather can be problematic.
As a side note example, many smaller bonsai (small ornamental trees) shippers do not ship in very cold or very hot weather...... especially Temp control in this packaging is not a primary concern, but the packaging materials are often insulating (think styrofoam peanuts). The boxes are usually marked LIVE PLANTS from reputable vendors, but still very cold or hot weather is avoided to prevent roots being frozen or cooked while traveling.
Perhaps Live Fish get further special handling that a Live Plant designation does not or is it critical to get really really good insulating packaging material or.....
Note am not thinking of shipping fish but of having fish shipped to me but want to avoid making a fatal mistake in getting tank mates for my 10 discus.