I keep my spares "hoard" In my garage attic which is warm and dry for almost all year except cold maybe in winter but still dry. (Cavity walls with tiled roof)
For long term storage of ECU's what's the best method? Zip lock bag with a small packet of disiccant silica gel? Or just in a cardboard box? Little relays I'm not so concerned about it's engine ECU's. I'm afraid the pins might corrode or moisture get inside after years of storage.
On the subject - how about petrol injectors? Plastic Tupperware box with some light oil in it such as wd40? Or store them dry in little baggies?