It depends on the style of the beer. For your basic american pale ale, it wouldn't bother me one bit. Once the fermentation is done, it is done and the basic fermentation profile is locked down. There's no magical reason why 70-75F is okay for bottle conditionning, but not for the tail-end of primary fermentation. Sure, lower temperatures are better since they will intice the yeast to flocc out more, but it's not the end of the world.
For English beers, I allow 2-3 days MAX of 72F + temperatures because any more than that and I get a flat, lifeless beer because the yeasts actually clean up too much esters. These beers are low-gravity, subtle affairs though.
I'd say that the ambiant temperature is less detrimental (to a degree) than fluctuations in the temperature. You don't want wild swings because it might stress the yeasts.