How long should the treatment be?
Approximately an hour is fine if your desired outcome is general relaxation or concentrated therapy for certain areas. However if attention is needed for specific muscles, there probably wont be enough time to cover the whole body.

How often should I have a massage?
Regular maintenance is advisable.

Does massage hurt?
There is a fine line between therapeutic discomfort when a knot is worked on and just plain pain when the muscles tense to protect themselves. You know the difference. So you decide how much, if any discomfort you'll experience for a positive outcome. Working within your comfort zone can achieve great results.