3x a week or 5x a week

I swim an average of 30,000 yards a week. The way I get 30,000 is the question I have. Some weeks I swim three times and do 10,000 each day. Other weeks I swim six times a week and do 5,000 each day. I wonder which way is the most effective for training. I feel guilty when I only swim three times in a week, even though I have the same total yards. What are your thoughts on this. Is it better, worse, or the same to swim three times a week instead of six times? I don't know, I am just trying different things to figure out what the best way to workout is. I should also mention that swimming is the only excercise I do and when I swim 10,000, I usually need the next day to recover.