There are two of us. There will usually be either 1 or 2 bags from the 25ltr (I think) kitchen bin in the black bin when i put it out each fortnight. They aren't really 'full' full, normally though - it is more a question of getting anything smelly out of the kitchen. If I have been around and emptied the other wastepaper baskets, which I proably do once a month or so, then there will be 2, certainly - most of the bulk will be snotty tissues though.
We usually cook from scratch and compost and recycle a lot though.