Yes, I heard that "rule" and used to do the "keep ammo and guns separate" thing also, but that's mainly for keeping your younger KIDS from finding them, not thieves.
Thieves are another story, so stop kidding yourself: They'll find your guns and ammo regardless of where you "hide" them separately. And quickly. That's their job, and they know all your "hiding" places because most other people do the same thing -- "hide" stuff (rather than lock it up/bolt it down). ;-)
Put the guns AND ammo in the safe/RSC. It'll be safe from your kids (unless they know the combination) and not as easy for thieves to just walk off with. Win-win.
I also agree with the other poster -- in a climate-controlled house, you're fine. I live on an island and within seeing/hearing distance of the Gulf of Mexico (it's across the street). Water is EVERYWHERE here, and salt air with very high humidity. Sure, OUTSIDE, everything rusts/corrodes -- cars, motorcycles, building hardware, BBQ grill, wiring, fencing (you name it) -- but INSIDE, the stuff in my 2 safes is fine...no dessicant and no Goldenrod used. Yes, if I leave the door/windows open for long periods of time, salt air and humidty can enter my living space do their damage, but I don't leave them open (I don't need to leave the AC on 24/7, either, just now and then to cool down the place/remove any humidity inside, then fans are used mostly). The MAIN thing is to keep the doors and windows closed! Yeah, I go out on my balcony whenever I want, but I close the door to keep the high humidty/salt air out (which will be good experience for when I move to Hawaii -- same salt air/humidity and rusting/corrosion issue there).
Ammo is in GI-issue ammo cans and guns are put in the safe as they are. You could use chemically-treated gunsocks if you wanted the added protection, and put a small pkg. of dessicant in the ammo cans if you wanted, but I don't do that myself.
No problems and I've been here 2 years now (including Hurricane Ike), and the guns WERE just in my closet before I got the safes. But even when they were in the closet, they didn't rust in a climate-controlled environment...it's just that "hiding them" in the closet made it too easy for thieves. ;-)
-- John D.