It sounds like Blight. Any chance to upload pictures? I'm not an expert and esp. am not familiar with Florida environment. But attached is a link you can review.

In particular, here are some quotes that struck a chord when I read your post:

"trees have extensive dieback but do produce interior shoots of new growth. Blighted trees usually do not die, but remain in this chronic stage."

"As the tree declines, vegetative sprouts may be produced on the trunk or on larger interior branches near the trunk"

"[certain rootstocks] ... usually do not exhibit symptoms before trees are 15 to 20 years old"

"Blight is found in mostly tropical or semitropical regions with moderate to heavy rainfall but is not reported in more arid regions such as the Mediterranean Basin and California. Blight has been present in Florida for more than 100 years"

Here is a link that might be useful: Univ of Florida Ext

Thanks for the help. I am 95% sure you are right. I looked up all the details and photos on the internet and it matches my problem exactly. The interesting thing is that I have a 7' navel orange tree that when I moved in about 6 years ago was dying. I now realize had the exact same problem. I trimed it way back as a last resort. It recovered in about a year off the fresh interior shoots. Now it's doing well. I guess I will give it a try on one of these soon - what can I lose.

- John