He is referring to the flaps in the VTCS system and BL is the code for second generation Mazda 3s, BK being first gen. Although I believe these names are only used in Australia.
To answer your question there isn't much you can do in terms of preventative maintenance other than remove them entirely as they're pretty much sealed inside the intake manifold. I'm pretty sure they fixed the issues causing them to fail by 2009. My 2008 2.0ls flaps had no free play and the rod was in perfect condition when removed, this was in a car with 220,000 kms so you should be fine.
Craig's video on his Ford Mondeo (I'd link the video but can't as I don't have enough posts on the forums.) showed the issue to be the small plastic inserts between the intake runners. These weren't present on my manifold so I doubt they would be on yours, I only removed my flap assemblies for the slight performance benefit which is actually quite noticeable.
But yeah you should be fine, and no, there isn't much maintenance you can do.