Not all workouts are created equal
I’m not going to overwhelm you by explaining the theories behind training principles. But it is important to understand that there is a method to designing an effective exercise program. Not all workouts are created equal and when you have limited time you need to make sure you’re being effective. Your specific fitness level and your goals are going to influence the frequency, intensity, time, and type of exercise you participate in.
The frequency of exercise should represent a balance between providing your body just enough stress to force adaptation but also allow enough time for the body to heal from that stress. The intensity at which you train should be enough to overload the body so it can be forced to adapt but not so much that it causes overtraining. The type of workout you participate in is largely going to reflect your goals and what you have access to, while the timing is going to reflect your current fitness level. Ideally an effective exercise program will hold you within a target zone for 20 to 30 minutes; beyond 45 to 60 minutes there are diminished returns.