Can you reinforce holes in the knees of jeans that are already there?

I want to buy a pair of 510 Levis jeans and they come with holes in the knees (intentional). I have never had hole in my jeans before, but this certain wash is not available any other way. One review on the site said that the holes widened whenever he bent his knees. Is there a way to keep the holes reinforced and at their current size and shape?