Great game, it reminded me how bad I am at microing in RTS games! The best strategy that I found was waiting for a fire to spawn a new fire, then just putting out the new one as they take a lot less time and water to put out. It is a very micro intensive strategy though, so I think it's well balanced. My favorite level was the one with the bush on the little island. I did a massive double take when it just spewed fire all over the mainland, great way of introducing the effect of the bushes!