Actually, in my experience with tokays, they don't reach full size until they are about 18 months to 2 years old. It is usually during this time that they sexually mature.
I've tamed plenty of tokays who were already adults so it is never too late. I've also had tokays who never accept being tamed however, the work done on them to tame them helps to take the "bull dog" edge off them.
I start working with a tokay using big thick gloves (did I emphaze that enough), holding them firmly until they quit thrashing. That may take up to two weeks of work. Once they start accepting that they will be held, it will take another four to eight weeks of holding them -- I usually do this watching TV which they will join in, they prefering action shows and movies. Usually somewhere in the four months of work of just holding them they figure out that I am not going to eat them (big fear they have) and that I am about 98.5ºF which conviences them that I am a warm moving heat source, and suddenly one day I am their best friend.
Never attempt to tame a tokay that is not acclimated to a new home. Acclimate first, then attempt taming.
All that is a very, very brief explination of how I tame tokays, and I take no responsibility to any harm that may come to anyone who attempts to tame tokays. I have tamed more than 30. I do have all my fingers -- somehow.
For pictures of cooperative and non-cooperative tokays, take a look here:
http://www.daygecko.com/html/tokay_geckos.html