I believe that in the beginning of a relationship, the submissive should be permitted orgasms as frequently as she wishes, although they should be limited to occasions in which she is being used by her Master.

This will enable her to associate the pleasurable feeling of the orgasm with the necessary early bonding period in which she learns her Master's requirements, rules, preferences, etc.

Later, as the relationship develops, I find that denial and deprivation work quite well (for short periods of time) in increasing the sub's willingness to perform and expand her limits, as well as increasing the enjoyment for her through the added intensity.

Denial = willingness to expand limits = greater reward for expanding limits thru more intense orgasm = future willingness to continue to expand limits.