The water conditions that I keep my cichlids?

As long as you aren't over stocked, I suggest sticking to the 25% change once a week. That gives the fish fresh water more frequently without disturbing the parameters in the tank. Try to avoid 50% water changes, with a healthy tank you should never have to do a 50% water change and if you do you have too many fish in your tank. A water change that big will effect the pH and temperate in your tank too much and may cause harm to your fish. 40% every 2 weeks is fine, but going 2 weeks without a water change is too long for a freshwater system in my opinion.