When I trained for the Europa Super Show last year, I did 3-a-day workouts for 18 weeks, and dieted for 23 weeks.
I did HIIT in the morning for 20 minutes. I lifted in the afternoons. I did HIIT and the hot tub in the evenings. Sometimes, I'd walk the shoreline late at night.
It can be euphoric to be in a high state of conditioning. You have to LIKE working out, and it helps to have a goal, like a contest, or a certain weight, or a certain fitness level.
It takes a love of being an athlete, and it takes a lot of discipline, as well as a ton of calories to train with such intensity and focus, but, that's what separates the men from the boys.
Here's a picture of those 18 weeks, and some ice cream (which smoothed me out a bit).
What neophytes often don't understand is that it's not really work / a chore for an advanced athlete and that we do it because we love the way it makes us look and feel, and we love how we can manipulate our bodies via discipline, nutrition, science, training technique, patience, and time. We do it because IT FEELS GOOD.
Twice a day is not to much, as long as it's not to much for you, and as long as it makes you happy and makes you feel well and the rest of your life doesn't fall apart.
You can lose 10 pounds pooping and sitting in the sauna for 10 minutes, just FYI. It's not uncommon for a person to bounce around 7 to 10 pounds on a DAILY basis.