That's what I do. With me and my fiancee, she flies less than me, so if we go away to a hotel / car rental etc., I claim the points for it, because I fly a damn sight more than she does. Besides, I usually pay for the hotel / car rental anyway, so they're 'my' points, technically.
But there's nothing to stop me getting an upgrade for her ; we do it this way, because I earn more points than her per annum, so it makes more sense.
Same with QC lounge access - she accompanies me as my guest, instead of me shelling out for annual guest cards, because I hardly get chance to invite anyone else into the lounge with me. She may come with me a few times a year, and so I always have enough guest passes.
I'm ever so good to her. 8)