The main thing is to keep the main o-ring clean. If its a red o-ring (which I believe it is) it's made from silicone rubber. Do NOT grease it. Over time it will absorb grease, become more plyable & elongate. Just running it thru your fingers to grease it will eventually stretch it to the point where it will be too long for the housing. Lub it with water & keep it clean. Remove it from the groove when necessary, otherwise leave it alone. If it does happen to be a black o-ring (neoprene) then it does require a light coating of silicone grease from time to time. Don't over maintain your o-ring.
I would also suggest that you test dive the housing without a camera inside. Dive to a moderate depth & work all the controls several times - push, pull, rotate... anyway they can move. I would carefully remove the main o-ring before doing this, clean & reinstall. Then follow the suggestions above.