I have always allowed my red wines to breathe for at least 45 minutes prior to pouring.  Often I don't drink the whole bottle, but instead cork what is left.  When I go to serve on a different day, does breathing the wine provide the same benefit?  Is it recommended each time I uncork the same bottle? 
I don't think so.  (I also assume that you are talking about dry red wines.)  You let the wine breathe to allow 1) things that need to evaporate to leave, 2) some air to be dissolved in wine.  Which is why wine tastes so different before and after you allow it to breathe.  However, when you put the cork back and open the bottle again in a day or two, or even a week, the processes that ages wine for months and years does not have enough time to «unbreathe» the liquid (consume all oxygen and replenish the substances that evaporate during breathing).  Which is why I pour immediately from a previously opened bottle and let the wine stay in wineglass for a few minutes. 