I've run into a fair share of dancers who claim to practice WAY more than I do. Like, three times as many hours as I log when I'm on my A game. And then I see them "practice". And then I think maybe they are confused what actually constitutes practice.
Here's how to know if you are NOT practicing:
Are you talking to people? I mean, saying hi is one thing, but The Nod and a wave is probably good enough if you're really practicing. Unless you're discussing the lack of connection in your picture line with your partner, practice involves moving your limbs, not your mouth.
Are you watching other people practice? Besides it being weird, watching other people dance does nothing for your own practice.
Are you listening to other people's lessons? STOP IT. It's soooooo not okay. It's stealing. And creepy. But mostly stealing. Therefore, it is a sin. A DAMN SIN.
Are you watching YouTube videos? They are inspiring, but they are not practice. They are fun and inspiring. Like Pitch Perfect. I watched that... I didn't learn how to sing. Or beatbox. No matter how many times I watched it.
Are you in the studio? Merely being in the building is not practice. You could be drinking the crappy studio coffee while scrolling through Facebook for two hours with your dance shoes still in your bag.
Here's how to know if you ARE practicing:
Are you moving your ass as perfectly as you know how? Even if it's not that perfect, your continued attempts at faultlessness IS practice. Improving your posture, frame, footwork, and techniques specific to one style or dance to the best of your ability/knowledge pretty much defines "practice".
Are you sweating? It's not necessary that you sweat, but it's usually a good sign that you are working.
Are you in the studio? You don't have to be. I have done full-out rounds around my kitchen and living room. I've also practiced my rumba walks in the grocery store. Garages and empty office bathrooms are great practice spaces, or so I've heard.
Here's how to know if you should stop practicing:
Have you begun demonstrating any of the "not practicing" behaviors? You may have overstayed your motivation window.
Are you no longer practicing for perfection, or just to log minutes? Is that imaginary partner of yours compensating for your total lack of frame? Are you sure that those steps you're doing are real steps at this point? Are you listening to music that's actual dance music? Are you using the mirrors to your advantage? Are you wandering aimlessly, with the authority that wearing earbuds grants, around the floor? If you answered "the second one", yes, no, no, no, maybe, you should call it a day.
Have you been at it for over two hours? I've never seen a couple practice for over two hours productively. NEVER. For a single dancer? Give it one hour. TOPS.
In other words, 40+ hours a week in the studio is probably not making you the best dancer you could be. Four VERY FOCUSED hours of well-planned practice would probably do a lot more good. And then you could watch more TV.