Erm, I’m afraid there isn’t a one-size-fits-all answer to this question.
My best response is...
“The least amount of time it takes to trigger a positive adaptation in your physiology”
With the right level of intensity this can be surprisingly short. Most of my home workouts are done and dusted in well under 20 minutes. Same with my online training clients.
Once this positive adaptation has been triggered bludgeoning your muscles with more and more exercise is simply adding extra fatigue with very little (if any) extra benefit.
Remember you shouldn’t be exercising with the sole intention of burning calories.
Its depressing, soul-sapping and ineffective.
Much better to focus on the positive stuff which regular workouts are actually really good for like:
Building lean muscle and improving body shape
Enhancing muscular strength and cardiovascular fitness
Fortifying bones and connective tissues
Improving energy, vitality and longevity
Boosting brain health, mood and thinking
Prioritising fat loss over muscle loss (when losing weight)
This mindset liberates you from the idea home workouts have to be long to be effective.
Workout to get fitter and stronger.
Then crack on with the rest of your day!