Who is using training blocks such as 3 or 4 weeks training hard and one week easy/off? How is it working for you?

I was planning on 3 weeks hard, each one made up of: M (easy day), T and Th intervals (hard days), Wed (easy/alternative activity), Fri (easy/race prep), Sat or Sunday (longer ride or race). These 3 weeks would be followed by one week easy to moderate riding with alternative activities, then back to the 3 week block again.