By running your own experiment for 40 days, you can decide for yourself whether or not the practice is beneficial. Extended practice A noticeable level of mantra siddhi (power of the mantra) is said to come with 125,000 repetitions of a mantra (Such an extended practice is called apurascha...
Among the highest and intermediate siddhis, one often finds raising a vetāla; the procurement of sexual partners through the yakṣiṇī-sādhana; the obtainment of a magical sword (khaḍga); and the preparation of magical pills (guṭikā), eye ointments (āñjāna), and foot ...