Yes. Photographs taken of a client years after the Basic Ten Series show that changes are still present and structure improved. Keep in mind, however, that bodies change in response to life changes. Injuries, accidents, pregnancies, lengthy illnesses and emotional stress may cause a body to compensate and change.
Some people choose to come back for advanced work, but the intelligence that your body has gained from the Basic Ten Series is lasting, and this intelligence is also what the ongoing work is built upon.