Yeah having an even mesh isnt that important, I like to try to keep it clean and even as I find it easier to lay out when UV mapping, and I always have the niggeling feeling that a concentration/lack of geo might make a bit of a strange highlight at rendertime, dunno why just do!

Jr Who, on the pic you posted if you take the corner of the new square made by the new loop and then add an edge from that to the corner of the other you'll carry on the quad structure which is what I would do