Hi. Yes, rear drums brakes are self-adjusting, but they're seldom called into use, so don't think they'll be much adjusting for a long time to come. Cleaning the build up surface rust may be necessary owing to the little use, but if you don't hear any unuaul 'scraping noises' I'd say don't worry about it. I hear Prius owner's complaining about the fronts rotors rusting.

Cabin air and intake air filters are every 30k.

All this is in the Bentley Toyota Prius Repair and Maintenance Manual. http://www.bentleypublishers.com/product.htm?code=TP08&ticket=ST-2634-uiGXaPByvUNla56gAXdF

Hope this helps.