Don't put full loads on them until they're 4 years old. The growth plates in their legs won't be mature until then no matter how big they are. Overloading them too young can do serious damage to their legs and greatly reduce their useful life span. Their size doesn't matter. It's age that counts.
You can google all kinds of info on how old they need to be. You're off to a good start with them. Don't screw it up by being impatient.
“In a time of deceit telling the truth is a revolutionary act.” ― George Orwell
It's not over when you lose. It's over when you quit.
