I don't have oodles of time to spend on the internet so I plan my time wisely...usually. My daughter does very well in school and completes all that is expected and more.
Most of the homeschool moms I know carefully prioritize their time, ensuring all that needs to get done, gets done. In addition, homeschool moms need time away from the school room - to refresh themselves. I'm hoping you encourage your wife in this way. :o)
From what I observed, she enjoys teaching him. I think she has found her life's bliss. I think Joseph Campbell had the best definition for it. "If you follow your bliss, you put yourself on a kind of track that has been there all the while, waiting for you, and the life that you ought to be living is the one you are living. Wherever you are -- if you are following your bliss, you are enjoying that refreshment, that life within you, all the time."
So, to answer your question, I do not encourage her to take time away from her true enjoyment. I'm just ecstatic that she is happy.