1) Abs are made in the kitchen. You need to spend a lot of time on the treadmill to burn off a single doughnut. If you skip the doughnut, you can skip the treadmill.
2) Each morning I do one set of pushups, curls, overhead press, lat pulls, and triceps. Probably takes less than three minutes. Back when I went to gyms, I would do 3-4 reps of 5-6 different lifts about twice a week. With travel time, rest between sets, and a shower that would take close to 2 hours per trip. So if you do the math, I am getting 7 reps of 5 exercises per week with a total time of about 20 minutes now vs 6-8 reps of 5-6 exercises per week for a total time of 4 hours. And if you do the math on total elevated heart rate time, the numbers are probably close enough, as there is usually a 10-20 minute recovery period after each workout. If we assume 15 mins, you get 7x15=105 minutes vs 2x(~40+15)=110 minutes. Basically in the ballpark even if the numbers are off a bit.
3) More importantly, I rarely skip the short workout whereas I would regularly skip the gym workouts. I definitely don't feel as good as I did after a gym workout. But I never feel as bad as I did after skipping the gym workouts for a few weeks in a row.
It is worth mentioning that I am not a disciplined eater. So I do go for a 3-4 mile run once a week, a short bike ride 1-2 times, and usually mix in another outdoor activity or two on the weekend. But just in terms of substituting gym time, I think the short daily workouts actually get you most of the way there. I am probably going to start mixing in an afternoon routine as well because it has been such a good development.
I have been applying the "maintenance" attitude to a lot of things as well as exercise too. My whole approach to household matters is informed by this now - I think about most my consumer purchases in terms of the "low intensity, high volume" use case, and measuring what improves my life by looking for benchmarks that would improve passively by having the item. Best ROI here is to spend on storage, organization, and ergonomics, because that lets you assemble a workspace for something much quicker. Assigning some things to a tray or bin can make all the difference. If it's shoved in a pile, the activation energy goes way up, rendering everything you already have relatively less useful. This is true even if you barely have any stuff to begin with!
Obviously the trick is making smart choices about that one meal, which isn't as difficult as I thought it might be.
If you’re starting from zero I wouldn’t suggest max sets, though. Start by trying to get the form correct. It can take some time to learn to recruit the right muscles. Watch a couple of YouTube videos and then film yourself to spot your deficiencies, correct, repeat. Still under 10 mins every other day.