Many states with a two year renewal cycle like Florida require 30pdh hours to renew so going to 18pdh is not too stringent in comparison.
Are there really any engineers out there though that forget how to be ethical every two years and need a refresher. Who really thinks "man, I almost thought it was okay to lie, cheat, steal, mislead, misrepresent, bribe, ignore the code, issue someone else's design as your own, get a kickback from a contractor by letting them put in substandard or lower than bid level installations, advertise you have experience that you don't, sign drawings you did not review and have only heard the project name once at a ball game, ... , but I just had that ethics course refresher and realized it was wrong so I didn't do it". Really???
Are ethics rules really changing that fast that we need a refresher on them every two years. Um, no.
At least the state of Texas will give you and anyone a freebie ethics course a few times a year if you want it:
http://www.tbpe.state.tx.us/webinars.html
I think it meets Florida's requirements.