Squee, they're not Canon housings, but I do the same O-ring proceedures on my Aquatica and Ikelite housings (and on the Nikonos):
I have two sets of O-rings, "Storage" and "Dive".
Each set has their own personal ziplock baggie.
The camera is stored, transported, etc. with the "Storage" o-rings in place. These will eventually deform from the constant pressure. This makes them unsuitable for diving, but they are good enough to keep dust, moisture and other things out. Most importantly, they act as a "cushion" between the housing halves, so bumps and jars do not
ding the sealing surfaces.
When setting up the camera for diving (read as "daily o-ring maintenence") I'll put in the "Dive" o-rings.
If diving over consecutive days, I'll just leave the "Dive" o-rings in place.
Your housing is small enough to be left wide open when stored, thus avoiding the damage from the two housing halves impacting each other. This leaves the chance of contamination in the o-ring tracks, for example, from the foam in a Pelican case. If you're comfortable with cleaning carefully, it's a good way of avoiding the percieved hassle of two sets of o-rings.
FWIW, my Nikonos is about the size of a small digicam housing...and I use storage o-rings on it.
All the best, James
