This just me, but... I change the Cabin filter every spring, as the air is most polluted with pollens. Depending on the air, where you live, you may need to do this more than every 12 months. The engine air filter, you should be running a 'drop -in K & N' filter. This really works, for me, but this is a personal prefference. I have had excellent results, IMHO, doing both of these service items.
__________________ 2014 ES 300h; Nebula w/ Parchment & ULP w/ ML & Navi
In previous cars, my cabin filters barely last a year living in L.A. I should have replaced the one in the ES last month but I've been lazy. I usually buy from ebay since you can find them for a fraction of what the dealer charges.
I personally would get Wix or whatever is comparable to OEM. Ever since Honeywell bought Fram, their quality has suffered significantly, especially their oil filters. For the northeast a cabin air filter change every 20-40k miles would be suitable. If your in high pollution areas or the south/west such as Cali, Texas, Florida I would check and/or change it every year. You can change the cabin air filter through the glovebox. Very simple, just open the flap pull out and replace. The air filter is one of the easiest I have ever seen.
2013 Lexus ES 350
2007 Audi A8L W12 - 6.0L
2005 Audi A8