You do have to find a balance that works for you. I was doing a lot more cardio and strength training when I was losing, and even since I've been on maintenance, I go up and down on how much I can fit into my schedule. Like you, I get busy at times and just can't do as much. I think you just have to continue to monitor your weight. If you start to creep up over your comfort zone, decrease your intake, or up your workouts. I think if time is an issue, you have to up the intensity rather than the total time. You have the right idea w/ the hiit, and tempo runs. I think it's all individual, and we all find the things that work for us. I don't do anywhere near 45 mins a day most days (more like 30 mins, but high intensity) and I've been maintaining 2 and a half years now.
highest weight ever:202, SP starting weight: 143
New goal: 125 lbs, just to see what that looks and feels like! Hit it: Feb 2013!
H: 5''4" 49 y.o.
"Don''t let yesterday use up too much of today." Will Rogers
"Eat Food, Not Too Much, Mostly Plants" Michael Pollan
| current weight: 9.4 over