One of the key things is to scale according to your ability to retrieve coins. There's no sense having high producing dragons max out and production coming to a halt. In my present situation I'm online *a lot*, even at night. But I found that three high producers in one habitat exceeded my ability to retrieve coins. For example, 3 Panlongs in an Earth habitat reach the $75K limit in just over an hour, which is too fast even for me in my situation. So I place two Panlongs in each Earth habitat along with some lower producer. Same with Cold habitats - I only have two Bluefires and/or Frostfires in each habitat.
That's the reason I had to take apart my Nursery Island for a time. I needed all the habitats for the CGCF.
Poppy