I would say with a 25% speed setting it takes 5-6 hours or so for the cooling effect to stop. This include finishing the tank from full and drying fully the wet filter inside the gadget. I don't know if faster speed setting (which are too noisy for me and do not improve the comfort level) would drain the water much more quickly.

I do not own The Smart version and I cannot comment on its cooling effectiveness. I remember I choose not to buy that version because I planned to keep it on my desk: no need for WiFi controls in this setup. Might make sense if you plan to keep it for example in bookshelves behind you, a little higher than your head, so that the cool air falls on you. But generally speaking you find your favourite setting and you don't touch it again.