As I go. That way I won't destroy my back by sitting on the floor for long periods of time to do them all. My mother prefers the "all at once a week before" approach, though (she wonders why her back is messed up afterwards).
Well...wrapping as they are purchased would make a whole lot of sense...and prevent the paralyzing Christmas wrapping bad back...but...alas...Mr s picks a night...puts on Bad Santa...and wraps...and wraps...and wraps...and then wraps some more.
No, I like to wrap mine in batches. I'll probably do some this weekend. I enjoy doing this either by myself or with a family member. I like to put on Christmas music or a Christmas movie while I do so.