I have spare PICs of every kind that I use, spare fuses for each type of controller, spare triacs, spare optos, spare sockets (mostly got those in case I messed up during assembly), extra resistors, spare PCBs for Dongle and EXRX, even spare built and tested EXRX and dongles. I also usually try not to use all 16 channels on an LE when doing setup if I can so I end up with spare channels in case I need them and I have needed them at times. It is pretty cheap to add another $10 of stuff to a Mouser order when shipping is going to cost so much later on if I need to rush get a part during the season. And other than PICs, most of the stuff is pretty inexpensive.