A: Thank you for asking this question. Many of my clients have expressed this secret fear!
What can happen with vigorous stimulation and/or repetitive programs of stimulation (that have always worked in the past...) is that the penis and ability to become aroused by the same repetitive means can become too predictable and numbed. The "spark" begins to fade.
Along with the many exercises and arts we teach in Tantra, we encourage students to explore different ways to experience and feel touch--different kinds of touches, varying in attitude, quality, pressure, and tone. This opens up a whole new, limitless universe to explore in the realms of loving one's self (and also another) through adventures in various, unpredictable combinations in a dance of touch that will breed a deep physical/emotional/spiritual interaction that never grows stale. This is the dance that will feed the "spark", making it brighter and brighter as your sexuality matures.