Try the link below from Lycheesonline...Also what part of FL do you live in? did you have a warm winter...I had plenty of "chilling" weather for my lychee tree but I live in Central FL. I think trimming around the middle of July is suggested...Try the trimming tips. It worked for me last year, though my tree is only 3 years old...its produced 2 years in a row...not sure if its luck or the trimming lol...

As for your seedling grown lychee they can take a lot longer to produce than air layers or grafted...but I'm sure it won't be too much longer.

But, keep in mind even though you do all the right things....lychees are known to skip a year or two depending on your location and variety...sometimes they just won't produce no matter what you do :o(

Here is a link that might be useful: Tips on Getting Your Lychee Tree to Produce Fruits