I really, REALLY hate the myth that your skin can "get used to" a product. I do believe that you may gradually build up a tolerance to certain ingredients (over years) but I don't think it's going to just stop working after a few months. So maybe in a few years, you may want to find a product with a higher concentration of ingredients that work well for you.
What I really think is that somebody in marketing made this up to increase sales. Or lots of people at the counters made it up to "explain" why a product "stopped" working, to make more sales. It's just a selling ploy.
I don't believe a "BB cream" is really anything more than a new name for a tinted moisturizer (usually with SPF)? All of the ones I’ve seen claim to brighten, hydrate, protect, prime, etc…all of which is what a tinted moisturizer does as well. It isn't that I want companies to stop producing them, or creating new products or TMs (especially since the ones I've seen have been generally pretty good) it just generally bothers me that they felt the need to call them “BB creams” instead of tinted moisturizer, to capitalize on the craze. It feels like another marketing gimmick. I suppose as long as it's a good product, I shouldn't care.
This is a comment I made on John Su's blog, The Triple Helix Liasion, as LadyIsla. Sidenote, John's blog is incredible! (edit: he's stopped posting...):
Calling these products “BB Creams” is just creating another needless category of products, like Eye creams, Neck creams, etc. Some Western companies are bringing out their own versions of BB Creams now, and if they manage to make another good tinted moisturizer, that’s great; but I am pretty much fed up with the endless marketing ploys, just slapping new names on a slightly different product. I do admit, it is nice that the items that are named “BB Creams” do tend to include an SPF and moisturizer, but it’s still annoying to me.