I am by far Runner then Cyclist and the Swimmer
And really I have left my running training equivalent to what it was before biking and swimming. Mostly because I know that I will make fairly good leaps just swimming in general 3-4 times a week, and still running 40-55 miles a week. I know if I swam 2 more times a week it would get sloppy and I would probably cut back my running. Therefore my swim wouldn't gain as much to the work input and I may not be able to reel people in like I do on the run.
On the otherhand, I have been bumping up the biking because I realize that most of the extra time spent on the bike is good time that is returning good increases.
What I am trying to say is that don't just workout to workout, as I have called them "junk miles". If you can only get so many good workouts in of a certain discipline don't force it to the neglect of your current strong points; this would be swimming for me. However, if you're ready to step up a discipline to the next level to match your best then a little cut back isn't bad; this would be cycling for me.
Just my theory, not for everyone