Were you stuck with 2.4GHz for a reason? I can't imagine how bad that would be in an apartment.
It's still amazing to me, though, that so much new gear is still 2.4GHz only. I bought a brand-new, top-of-the-line air filter earlier this year, and even at close to $500, 2.4GHz is the only option.
With an air filter, do you ever want to control it? Naively I'd think that you'd want to leave it on unless you're going to be gone for a week or more. And even in that case it's probably easier to flip the switch.
Would it tell you when it needs a filter change? Would that actually work better than a calendar?