I think Ten minutes is already enough when your just maintaining your body but you should do this daily. But if you want to tone your body more then you should consider working out more than that.
When you are on the go or there's no time to go for a gym i suggest shadow boxing or just static running. It's easy and flexible in terms of space, you can actually have your 10 min. exercise almost everywhere.
If you are a stable weight then the exercise is not needed to maintain body weight. You can do that purely with diet.
But exercising is important for more than weight...
It will make you stronger, fitter, make you look better and live longer. 10 minutes is not enough though.
Maybe you are right with saying that 10 mins. exercise is not enough for a more weight person. But if the person have a normal weight, the 10 mins. exercise are definitely okay especially if it will be done everyday.
I am into a 3-minute exercise every morning just to maintain my weight even if I am still overweight. But I guess the stretching, bending, using the dumbbell and the hand grip exerciser should be for a longer time. Maybe 10 minutes a day would be fine but it’s just not very possible for now since my work schedule in the office is very early. For me, maintaining the weight is more of the diet than exercise. When I eat more, expect my weight to increase regardless of the exercise that I do.
10 minutes exercise is good, as long as your body is moving and your burning fats.
What will you do in 10 minutes? Start stretching and do 10 minutes walk or jog a day and it will make difference for sure.