Hey armout, thanks for taking the time to read my post!
When talking about the concept of time within dreams, one must distinguish between physical REM sleep period measured in units of time (i.e minutes lets say) and the subjective sense of time, felt from within the dream by the dreamer. Now here is where it gets interesting. I found in my own explorations that the subjective sense of time can be stretched immensely, even within the physical boundaries of dreaming, which are yet to be fully understood. (As said in the post, dreams can occur in NREM sleep too so, although you do have micro awakenings, so staying within the same dream for too long in the real world is yet to be determined feasible)
So what I'm getting at here, is that by increasing the lucidity levels and how in control/aware you are within your lucid dream, you can stretch the subjective sense of time for you, to feel like your lucid dream was a day long, in what you conceive to be a 'day long' in real time. Does that make sense?