I carry a different bag every day. Someone suggested on TPF awhile back that at the end of each day, she puts all of her items in an LV box in her closet and restuffs her bag and puts it in it's sleeper home/dust bag. That's what I do every day as well. I treat it as I do my shoes. I put them in their box, as well.
I change a couple times a week but i usually don't change my wallet, makeup bag,etc...the only time I change my wallet is if I am using a smaller bag that my wallet doesn't fit into...
i change depending on the outfit and occasion. but i usually never change my wallet (unless it's a special occasion requiring a clutch or some other tiny bag).
I use one bag/month (may vary it for a special occasion) and it's based on color.
For example. Feb is Burgundy month. SO.....I use my Bordeaux Twiggy, burgundy Prada glasses, burgundy band on my Techno watch, toenails stay burgundy the entire month, and for the entire month there has to be burgundy somewhere in the clothes I wear.
I change according to my outfits