Muhammad Al-Hurr Al-Amili writes:

وَأَمَّـا أَحَـادِيـثُ الْاِثْـنَـيْ عَـشَـرَ بَـعْـدَ الْاِثْـنَـيْ عَـشَـرَ فَـلَا يَـخْـفَـى أَنَّـهَـا غَـيْـرُ مُـوجِـبَـةٍ لِـلْـقَـطْـعِ وَالْـيَـقِـيـنِ لِـنُـدُورِهَـا وَقِـلَّـتِـهَـا وَكَـثْـرَةِ مُـعَـارَضَـتِـهَـا كَـمَـا أَشَـرْنَـا إِلَـى بَـعْـضِـهِ وَقَـدْ تَـوَاتَـرَتِ الْأَحَـادِيـثُ بِـأَنَّ الْأَئِـمَّـةَ اثْـنَـيْ عَـشَـرَ وَأَنَّ دَوْلَـتَـهُـمْ مُـمْـتَـدَّةٌ إِلَـى يَـوْمِ الْـقِـيَـامَـةِ وَأَنَّ الـثَّـانِـيَ عَـشَـرَ خَـاتَـمُ الْأَوْصِـيَـاءِ وَالْأَئِـمَّـةِ وَالْـخُـلَــفَـاءِ وَأَنَّ الْأَئِـمَّـةَ مِـنْ وُلْـدِ الْـحُـسَـيْـنِ إِلَـى يَـوْمِ الْـقِـَيَـامَـةِ وَنَـحْـوَ ذَلِـكَ مِـنَ الْـعِـبَـارَاتِ فَـلَـوْ كَـانَ يَـجِـبُ الْإِقْـرَارُ عَـلَـيْـنَـا بِـإِمَـامَـةِ اثْـنَـيْ عَـشَـرَ بَـعْـدَهُـمْ لَـوَصَـلَ إِلَـيْـنَـا نُـصُوصٌ مُـتَـوَاتِـرَةٌ تُـقَـاوِمُ تِـلْـكَ الـنُّـصُـوصَ لِـيُـنْـظَـرَ فِـي الْـجَـمْـعِ بَـيْـنَـهُـمَـا وَقَـدْ نُـقِـلَ عَـنِ الـسَّـيِّـدِ الْـمُـرْتَـضَـى أَنَّـهُ جَـوَّزَ ذَلِـكَ عَـلَـى وَجْـهِ الْإِمْـكَـانِ وَالْاِحْـتِـمَـالِ وَقَـالَ لَا يُـقْـطَـعُ بِـزَوَالِ الـتَّـكْـلِـيـفِ عِـنْـدَ مَـوْتِ الْـمَـهْـدِيِّ عَـلَـيْـهِ الـسَّـلَامُ بَـلْ يَـجُـوزُ أَنْ يَـبْـقَـى بَـعْـدَهُ أَئِـمَّـةٌ يَـقُـومُـونَ بِـحِـفْـظِ الـدِّيـنِ وَمَـصَـالِـحِ أَهْـلِـهِ وَلَا يُـخْـرِجُـنَـا ذَلِـكَ عَـنِ الـتَّـسْـمِـيَّـةِ بِالْاِثْــنَـيْ عَـشَـرِيَّـةِ لِأَنَّـا كُـلِّـفْـنَـا أَنْ نَـعْـلَـمَ إِمَـامَـتَـهُـمْ وَقَـدْ بَـيَّـنَّـا ذَلِـكَ بَـيَـانًـا شَـافِـيًـا فَـانْـفَـرَدْنَـا بِـذَلِـكَ عَـنْ غَـيْـرِنَـا انْـتَـهَـى

“As for the sayings (hadith) about the twelve after the twelve (a.), it is not ignored that, because of their rarity and sparseness, they do not make it necessary to have any certainty and assurance about them. It has been continuously transmitted that the Imams are twelve, that they will prevail until the Day of Resurrection, that the Twelfth is the seal of the representatives, successors and Imams, that the leaders are from the descendants of Husain (a.) until the Day of Resurrection, and similar statements. If it were prescribed that we had to profess the leadership of twelve after them, then we would have obtained continuous sources equivalent to those sources, so that one could look at the agreement of both, and it has been transmitted by the Sayyid Al-Murtada that he considered this permissible within the bounds of possibility and thought, and he said: “It is not certain after the death of Al-Mahdi (a. ) to assume the end of the imposition (Taklif), but it is possible that after him leaders will continue to exist who will protect the religion and interests of their relatives and this does not make us abandon the title of the Shiites of the Twelve, since it is imposed on us to know of their leadership and we have made a clear statement. Thus we distinguished ourselves with exclusion from others.” End of quote.” [Al-Iqaz Mina l-Haj’ah, page 401]

Comment:

As-Saduq agrees with Al-Murtada on this point [Here!]