Well, I hate to say it, but I'm much too lazy to change my bag every day, or to match every outfit! In the past, I have chosen a bag and carried it for the month. As my collection grows, however, I am finding that there are not enough months in the year! So, I may need to move it to every two weeks or so. I sort of have my bags mentally grouped by season.
Obviously, if I am dressing for a meeting or some kind of special event I do take the time to change the bag to match the occasion, but not on a daily basis.