Yes. You will progress much faster if you do more workout time. You could do it as one long workout with a short break in the middle, or two workouts would be fine if that works better for you.
Just be sure that you don't wear your voice out. If you build your stamina and take things steady-as-she-goes, you should be OK.
If your voice gets tired, you are pushing too hard. Stay just under that limit of how much singing is too much or too strong for you at the time.