I’ve had this T-rex long enough now to write a brief review .  There are videos showing the features so I’ll stick to basic concerns prospective buyers may have .
I was considering purchasing a Garmin smart watch but figured I should buy a less expensive offering in the case I ended up not wearing the thing very often .

This watch is very light weight and I forget it is even on my wrist . It is large but very comfortable and I have a small wrist ; about 6 1/3 inches diameter .
The keeper on the band that secures the excess portion of the band beyond the buckle incorporates a small protrusion that interlocks with the holes in the band and prevents it from sliding around and allowing the band to flop free like every other watch band I’ve owned . I wish this was a feature on all polymer bands !

I charge the battery to 90 % and recharge it when it gives me a warning @ 10% charge .
It requires one hour to charge from 10 to 90% .
I use the GPS function twice a day for cycling for a total of maybe 1 hour to 1.5 hours total / day and operate the watch with the screen normally off and the battery lasts about 15 days , although sometimes it will go 23 days if I’m only wearing it 5 days a week .
I’m guessing it will last you at least 5 days if you are using the heck out of it each day , but it charges so quickly battery life should not be a concern .
I do not sleep with it so I cannot comment on those features . The GPS is accurate as far as tracking your movements on the map as well.
Overall this is a very capable device for such a low price . Very easy to operate .