It depends.

For example, today I did a 45 minute ride on the trainer, and it included some intervals.

Yesterday I did a 30 minute recovery ride. Intensity was around 65% of max heart rate.

Saturday I did 3 and a half hours at a pretty low intensity (~70% of max heart rate) -- long, steady distance.

Sunday I did 2 and a half hours at an even lower intensity. I'm training the California AIDS Lifecycle ride, so I'm practicing doing longer rides on back to back days.

-- Melissa