I have always preferred multiple smaller doses of opioids than less larger doses. I like the peak feeling/highest serum concentration/rush that comes with a fresh dose. If you are already tolerant of the total daily amount you are taking than dividing it into 2 doses rather than 3 should be no problem at all, that is provided you are not mixing with alcohol/benzos, etc. Also, the respiratory depressive effects of codeine are slightly less than that of morphine, heroin, fentanyl, etc.
I find that rather than ever increasing doses for the same effect, try tapering for a few days than go back to the dose you were taking. If you can get down to 75 to 90mg 3x daily and then increase back to the 400mg/day dosing you were taking; this is more desirable than creeping up to 500mg or 600mg to get the same effects. Your pockets will thanks you and your body will thank you by consuming less total medication. And the higher the daily usage the more difficult it is to get stop should you choose to.