I train in blocks and always end each block with a day totally off the bike then do AR day(s) until I'm totally recovered and ready to start the next cycle; it's just what works for me. I live in a very hilly area, so AR is constrained to the trainer. Basically, I go like Hell on the bike, rest like Hell off the bike.

Blocks can range anywhere from 3-15 days, depending. My focus is totally on time trials now, so I seldom do rides over 90 min, but the rides I do are (relatively) intense; I spend the majority of my ride time at Level 4 and above.