I'd say no more than 12 inches, if that's the maximum range you might feel threatened inside your house.
Is 25 yards a likely distance you might shoot in self defense in your house? I think in my house, I'd stick with 10 yards or so, maximum.
for utdoor use, 25 yards might be a good range to pattern I guess, but I haven't taken to carrying a 12 gauge for SD yet.