This was the opinion of Sheikh Al-Islām Ibn Taymiyyah, who said:
11 February 2025 • 2.22K views
«وَلَا حَدَّ لِأَقَلِّ النِّفَاسِ وَلَا لِأَكْثَرِهِ وَلَوْ زَادَ عَلَى الْأَرْبَعِينَ أَوْ السِّتِّينَ، أَوْ السَّبْعِينَ، وَانْقَطَعَ فَهُوَ نِفَاسٌ وَلَكِنْ إنْ اتَّصَلَ فَهُوَ دَمٌ فَسَادٌ، وَحِينَئِذٍ فَالْأَرْبَعُونَ مُنْتَهَى الْغَالِبِ»
"There is no minimum or maximum duration for nifās. Even if it exceeds forty, sixty, or seventy days and then stops, it is still nifās. However, if it continues uninterrupted, then it is fasād (irregular bleeding). In such a case, forty days is simply the predominant limit." [Al-Fatāwā al-Kubrā, 5/315]
Source:
https://t.me/Bashuaib/7507