haha I know I dont know nearly as much about boxing and toneing up as alex and adam do, but one thing I have learned is nobody can really tell you how much you need to do or how long or whatever, everyones different(which more and more people keep on doing, but I did it too when I first started so I understand). The thing I go by is pushing my self til I truly cannot go anymore, cuz as long as you push yourself as hard as you can go til you cant do anymore you will see yourself gaining more and more strength and be able to go longer and do more reps. So my suggestion basically is just go til you cant go no more, everytime.