Right, a couple of necessities is one thing, but just milking it just because you can seems like a dumb idea. If you have enough extra space in your bags to accomodate a ton of new stuff, you're carrying too big of a bag.
A 22" bag is 6-8 days worth. To Europe, 2 pair of shoes (wearing one), all black pants and sweaters, couple white shirts, tees for the summer, long sleeve for the winter. Packable ultralight down jacket. Most every trip I take the oldest undergarments, and toss on the homebound trip. As well as anything else nearing its end.
I don't require a ton of "beautification tools" (makeup, blowdryers, curling irons). So, no, my bags are not too big. I could carryon, but that's the choice I make to check a bag, and know what do do if lost/delayed.
I can go 4-5 days in a 17" roller board. So, no, my bags are not too big.