Good point. I make sure to hydrate before and after a "session." Furthermore, after a session, I try not to shower right away and let more sweat pour out. Not comparing it to cardio, which is also beneficial in terms of stimulating the lymph system and toning and strengthening the muscles, but I'm think the sweating/hydration principle is the same -- i.e., the need for adequate replacement water (plus electrolytes) and perhaps carbohydrates (I usually have carb-rich Daterade [sic] after showering) as well.
I've had it for about four months so I discount the placebo effect.