Hi Pat,
I think that this is a difficult topic to give advice on, because I am not aware that anyone has ever proved if on method is better than another.
Many photographers I know never clean their camera during a trip. Personally I clean my o-rings everytime I move them. It only takes a minute. And generally this means cleaning the main o-ring and port o-ring each dive. I like to change lenses for most dives as I find the new perspective of a different lens motivates me and makes me take better pix. It is just a personal thing. I tend to clean the synch cord every couple of days.
I have never had a flood with any of my slr (film then digital) housings. That said I have seen many camera's flood directly after being cleaned with people not seating o-rings correctly etc! I have also seen many o-rings leak when they were "fine on the last dive".
Another thing to consider are the diving conditions. If you shore diving off a sand beach, your o-rings will collect lots of sand, while if you are boat diving in open water they will probably stay very clean.
But as I said at the top I am not convinced that there is a right or wrong. I would suggest you should decide what routine you are going to do and then stick with it. That way should you have a flood you won't kick yourself for not doing what you planned.
Alex