Then why not have a card system for all of them on your fleet, if it is robbed put it down on the cardex system as to which aircraft it has gone to, have the system divided up into a twelve month period and those due in certain months put the card into that month with all details of what and when it is due, you can then trace the item to the aircraft it is in and check at the start of the month which is due......... not rocket science but it works..failing that put it all on a PC and at the start of the month call up what is due that month.
you could also mark each item with coloured tape or tywraps so you can see at an instant what month they are all due....... that way a quick visual check of each aircraft will help as well