Randy, that is a very interesting question. I'm sure you're right that it varies widely in different types of crotons and in different types of environments with different types of care. Way too many variables to make any solid assumptions, I think. However, it's so interesting that you've documented this and you should keep us posted each year and when it finally falls off! I'm going to try to notice the same thing in a couple of my plants also.
I have another question. Many, although not all, of my crotons are dropping a few leaves recently. Not a lot, but a few of the older leaves become discolored and then drop. I don't know if this is a result of the cold (the coldest night here was 37 for a few hours only), or just a result of the season and investing the energy into new growth with this present warm spell and longer days. My yard is just starting to get significantly more amounts of sun in the last week or two. What is your experience in your yard with old leaf drop this time of year? Am I the only one seeing this in my crotons now? I'm asking all of you!