The advise of how often to listen to the tapes is printed on the inside cover for each tape. It will depend on the goal and the tape. Fortunately the paraliminal tapes are more effective than subliminals and other tapes that require 30 days before you start to see some progress.
Keep a written record of the tape and the goal you focus on per session to help you to notice the progress you are making. It will also allow you to adapt as you need to.
The maximum number of tapes one can listen to in my option would be 3 and each would be related to the same goal- perhaps a stage or different step of the goal. Any more than 3 per day you would be showing your inner mind your doubts about it working and you mind has a knack of producing the results that you expect not necessarily what you desire. Secondly I think 3 would be the most since we theres more to life than just listening to paraliminals hours on end. If you have a number of goals to work on make a list and prioritise which goal you want to work on first. You'll want to work on this for a few days or week until you see yourself working in the direction of the goal. Then let it flow.You'd come back to the tapes or try a different tape if you stall.
Working on any more than one major goal (long term personal goals eg. developing new skills for learning) and one minor (short term goals eg getting into habit of making the bed everyday)goal at a time becomes self defeating. Your mind has to work out how to make your new habits fit, overload it with too many directions at once and it seems to go on stike and none seem to surface.
In any case leave at least 20 minutes between listening sessions. You can use different paraliminals to help you with different stages of a goal. Best keep a journal or logbook to see what works best for you.
Alex