In general, you can accept the pre-set treatment times for each programme. One treatment a day is more than enough in most cases. To give you an idea of just how effective a treatment session is: some therapists using the Elexoma only give ONE half-hour treatment session a WEEK and they still report dramatic results. If you insist on using the Elexoma for longer than the pre-set time, then it is better to give yourself multiple treatments during the day, rather than one single, long treatment. The reason for this is that a cell can only be stimulated so much and then no more. Anything beyond that is wasted effort. Rather boost the cells periodically and then give them time to use that boost effectively instead of boosting them continually.
An exception to the above: If you are using the Elexoma to help you with studying, it is recommended to use CES at a low intensity (say, 100 uAmp) for a fairly long period (an hour or more) while you are studying. This will keep you focused and help you lay down fresh memories that are easy to recall later.