Wow, you are really committed! I applaud you! You are doing 2-3 miles already on the ellipticle at a time? How long does that take? 40 minutes?
I personally wouldn't be able to do more than one workout a day without getting very tired and burning out. Right now I do 30-40 minutes a day, and I rotate that between the treadmill and ellipticle. I'm finding I get my very best workouts from the treadmill..... I switch between doing continuous hills during one workout, and on the next workout I might alternate between running five minutes and walking 30 minutes. Calorie-wise, the elliptical workouts show that I've burned more, but when I look at actual weight loss and toning, the treadmill seems to beneift me the best.
A couple times a week I add about 20 minutes of weights after the treadmill. Seems to work well.... I've lost about 15 pounds, and believe that I'm at my ideal weight and probably more fit than I've ever been.
Good luck to you, please let us know how you fare with the two workout a day... I'd love to hear!