I'm about 25 lbs overweight and I just got a home elliptical (Schwinn 430) that I absolutely love. I wake up and do 30-45 minutes in the morning, then another 30-45 before I go to bed. A couple questions here..

First off, is it as efficient to do cardio both early and late in the day, or should it all be done in the morning? Secondly, in 1-1.5 hours, I'm averaging about 6-8 miles in each day and burning 550-750 calories. I feel comfortable enough doing this, and try to stay within a heart range of 135-155 (my resting is about 72).. I was just wondering if this is healthy/okay to do 7 days a week, and will it be okay to increase to 15 miles a day when I'm able to?

A few notes (I'm not sure if they matter or not).. I'm 23, female, about 145 lbs at 5'3", and eat about 5 small meals throughout the day, starting with some fruit first before working out in the morning. I'm also trying a lifestyle change and increasing the amount of organic foods and less pre-packaged and processed foods.. I drink at most one soda a month, and my only fast food setback is taco bell once or twice a month (I know its terrible, but its a habit I'm trying to break! haha).. I drink about 12 big glasses of water a day, and some milk or juice at least once a day as well... For the most part, I stay away from foods high in saturated and trans fats.. its really just pasta, cheese, and chocolate I need to cut back on..

My highest weight was 184 at 5'2" and I went on the Atkins diet and got down to about 140.. Then just by watching what i eat better, I got down to 128 over about a year.. Get out of a bad breakup in the winter then head to the parents house for summer break out of college and I managed to get back up to 145.. That's where I'm at now.. I would do Atkins again, but it made me feel weak (I lost a lot of muscle with the fat).. I also don't eat much meat anymore besides fish...

Anyway! I'm really motivated to lose the 25 pounds and keep it off, get healthy, and feel better.. I know it takes time to come off, but in anyone else's experiments how long until I get some results? Any tips? Any answers to my two questions above?