Ok I just bought a new incubator the Hova-bator 1588. I just stuck my first set of eggs inside of it. For the past couple of years I have been using a brinsea octagon 10 for my hatches. Now I never had or used a hygrometer. I just kept those two little troughs in there full of water and never had a problem with hatches. The booklet that came with my new incubator said to keep the inner groove filled with water during the first 18 days and then filling both the outer and inner for the last 3. I guess my question is do I need to buy a hygrometer and keep a close eye on the humidity? Or is it not really as important as some people make it out to be? Again I never had a problem with the humidity in my other bator and never checked it. Thanks in advance for any feedback.