You can do a prelim OFA from 1 year up but will not get certification until 2 years old. CERF can be done at any age on the eyes they should also be done yearly due to changes in the eyes. Also, they say that Penn hip is more acurate than OFA. Great of you to be health testing before you consider breeding. Way to go!
The great thing about this health testing stuff is that it will provide you a solid guide within your breeding program to insure that no affected dogs genes will be used to create big problems generations down the road... as long as EVERY dog is health tested.
Here are the official applications for the OFA for the health tests that Cree is getting ready to go through over the next two months. On each of the applications the age requirement for the tests are in black and white. It is true that for the hips, elbows and patellas your dog must be 24 months of age, but the other health tests are accepted at a surprisingly young age.