Not a good idea. It doesn't re-circulate and freshen the water through a carbon filter. You would be better off just giving fresh water routinely like you are. It would take a cat a while to go through that much water and if any amount of sunlight can reach the location that is in, it stands chance of growing microbes if the water sits long. The drinkwell keeps water moving and through a filter, so it doesn't start to stagnate at all. It remains "fresh". They are worth the money.
If you have hard water in your area though(well systems) then invest in a brita to take hard elements out before putting in a drink well. Hard water will start scaling n the filter and pump system making maintenance more troublesome and lower the life of the pump.