i've heard of really great success using a continuous flow nutrient film. i'm not sure how deep your pots would be in the water if the water was allowed to flow continuously though. strawberries don't tend to do too well in very wet conditions whereas lettuce will do fine with roots submerged in well oxygenated water. a timer is probably a safer idea but nobody makes history by playing it safe. an optimum can probably be achieved by balancing flow rate and crown depth. I encourage you to do some science and report your results!