I always recommend testing when you have a question that you want/need to have answered. If you know what you need to know, then don't spend the money on testing. (But "Is s/he making progress" is definitely one such question. Periodic testing is definitely in our kids' futures for that reason.)

The other reason to test (IMHO) is if there's a program you think your child might like/be able to use. DYS, CTY, etc. If scores are required, then you'll do the testing.

FWIW...

Kriston