good question. i have read some about each and in the aeroflo2 directions it says 24/7. makes sense, dwc is submerged in w ATER CONSTANTLY SO I DONT SEE THAT BEING A PROBLEM. THERE IS QUITE A BIT OF o2 in the rail so we going to think u dont have to worry about enough O2 to the root. pump adds heat to res and so will the pump that is pushing thru the chiller. how much heat? some. get a good enough chiller and u will never notice the heat from the pumps. insulate your res and shade it from the light.
now why people have it on timer? because they probably havent ran the pumps 24/7 before. not having them 24/7 is creating a hybrid system out of a somewhat hybrid system. i dont think a hybrid is going to get better results, not as good i would imagine.
i suggest trying both ways and see what works best in ur situation...
im going to play with both ways only if the first way i try dont do well. if it not broke dont fix it.