Generally speaking shastras talk about doing 1,25,000 japa of any mantra to obtain mantra siddhi. And then Vedic Pauranic literatures and their guru traditions talk about other numbers derived from counting the number of beejas in your mantra, to decide the japa required.
But according to cosmic design, it is not so.
Depending on your spiritual journey number of jaap required to obtain siddhi varies. Generally Jati, varna gives perfect insight into spiritual journey of a jeeva, and accordingly number of jaapa required will vary to obtain a siddhi.
Gurus can directly do shaktipaat for any mantra, and in that case number of japa required to obtain kripa of any God decreases significantly, and sometimes if a jeeva has already done sadhana of some Ishta, that Ishta will continue to give his kripa even in this birth.
Below is a rough number, but if a sadhaka feels that mantra is not working, or desired kripa is not obtained after this number of jaapa, then he should continue the japa more number of times.
Japa siddhi is shashwat, but there is no method through which it can be determined how far a jeeva has achieved in their previous lives, except their present varna, jati, kula indicators.
Group 1 – Shrotriya Brahmins – Shandilya Tiwari, Gautam Mishra, Garg Shukla – 1,25,000 Jaap
Group 2 – Smartya Brahmins – Mishra, Tiwari, Dubey, Shukla of other gotras – 11,00,000 jaap
Group 3 – Shastreeya Brahmins – All other brahmins – 1,25,00,000 Jaap
Group 4 – All others – 7.5 Crore to 121 crore Jaap.
This is according to number of human births left in current cycle before a jeeva enters into 84,00,000 yoni cycle again.
Group 1 – last birth as human
Group 2 – 1-4 human births left before next 84-L yoni cycle begins
Group 3 – 1-6 human births left before next 84-L yoni cycle begins
Group 4 – 1-10 human births left before next 84-L yoni cycle begins
So no jeeva has to think that Oh, I won’t be able to get any anubhav in this life, so I should not do japa. You have to start in some life, why waste time? Every jeeva should give impetus to their spiritual journey today, and now.
Along with the mantra for which sadhaka wants to attain siddhi, they should also have done jaapa of Bhairava, Ishta, and Guru Mantra along with certain required beejas.
Sadhana is a journey of many lifetimes. It does not come easily, and does not come to those who want to bypass cosmic procedures. Some non-brahmin guru Parampara’s which have chosen wrong paths to obtain quick siddhis, end up destroying the spiritual journey of the jeeva, and hence should be avoided by all.
Adhikara is most important in trying to obtain kripa of any Ishta. Not every jeeva has adhikar for all kind of siddhis. Only devtas for whom jeeva has already done some journey in previous life, provide quick kripa, otherwise if jeeva is doing upasana, sadhana for the first time, then it is possible that this entire life they may not see anything, but if a jeeva attempts an upasana, there are divine bodies which will ensure that jeeva completes that sadhana in this or next lives, if jeeva remains firm in their resolve towards their ishta.
Those who start a sadahan and then run away from it, ruin their journey, make their guru patita, and at the same time cause immense injury to repute of their Ishta as well. Therefore always prepare yourself fully before starting any sadhana, and then give your entire life towards achieving pratyaksheekaran of your Ishta.