If used inside an insulated foam container, how long will these continue to operate near peak value?

For long lasting ice, save your 16oz water bottles. Fill them almost full with water and leave the cap just a little loose and put them in the freezer. When frozen securely tighten caps. Use the frozen bottles in place of ice cubes to keep an ice chest cool and they will last DAYS, and you can finish them off as ice water. I've done this for years and it' amazing how long they remain frozen.

does the product contain ammonia nitrate?

No they do not. the contain calcium ammonia nitrate. No good for tannerite. It must be a new policy

is this toxic waste or hazardous materials?

Here is the Material Safety Data Sheet for this product, provided by the manufacturer: http://dynarex.com/resources/MSDS/MSDS_Instant_Hot_And_Cold_Packs_(4511-12,_4515).pdfAccording to this: 'This material, if discarded as produced, may be a RCRA "characteristic" hazardous waste due to the characteristic(s) of ignitability (D001). If the material is spilled to soil or water, characteristic testing of the contaminated materials is recommended. To assure proper disposal, consult with state and local regulations and disposal authorities.'I called my local county Haz Waste office and the officer couldn't tell me whether Ammonium Nitrate was considered haz waste where I live, but requested I bring it in to Haz Waste for disposal. Although ammonium nitrate is a fertilizer, many agricultural chemicals are considered hazardous waste.

are they allowed on planes

Get an old fashioned hot water bottle, put it empty in your carry on and when on the plane ask the attendant to fill with ice. Put a little water inside, put it inside a plastic bag and it will last for about 30 minutes. Repeat! No waste, no cost!