You never do a 100% water change after the tank is cycled, that would be a complete waste of a month
The only time you change the water during a cycle IMO is if you are doing a fish in cycle. Or like dramaqueen said, when the cycle is complete and the nitrate readings are high, then you should do between a 30-50% water change before adding the fish and the fish should be added gradually to prevent a mini cycle.
Do you have a test kit? if not I would recommend the API freshwater master kit, this gives more of an accurate reading than the strips.