This is from Ramora, who have the contract to dispose of TEPs for the coastgaurd:
"The issues with storing up TEPs for an extended period of time is the licensing issues involved. When flares become expired they are all classed in explosive hazard division 1.2 as opposed to the 1.3 and 1.4 they are classed as when in date.
The hazard division relates to the most hazardous item that you are carrying. So if you are carrying one 1.2 item, the whole load would be classed as 1.2 and limited to the 50kg threshold. Ramora can provide you with Secondary Transport Mitigation Cages (STMCs), which mitigate the hazard of pyrotechnics, allowing them all to be transported at 1.4. This enables more items to be transported and also adds another safety measure to the transportation of pyrotechnics.
On top of these requirements, all explosive items that you are transporting would need to be in their original packaging. This is not an issue for operational pyrotechnics, as unless they have been removed, they should be in their approved packaging. When it come to TEPs, due to the change in their hazard division their previous packaging is no longer approved. Along with our disposal and training solutions, Ramora can also provide approved packaging for transporting TEPs."
I can give you the contact details of the person I'm dealing with if you need further clarification.