There's a little conflict between two Hadiths in the practice of some Imams!
One of them is telling us, that we should perform a longer sujjud during Nafl (#1) prayers (by extending the dua') the other is telling the Imams to shorten the prayer (#2 and #3)!
The preferred Sunna as far as i know is to do Nafl prayers as a fad this means (alone) for oneself. But people used to pray some prayers in a mosque following an Imam for example the tawarih (qiyam) prayer and the tahajjud in Ramadan.
Some Imams these days seem to like to show people how faithful they are and extend the sujjud, ruku' and dua' (dua' al qunut shouldn't take more then 1 minute!) but i heard enough U'lama saying this is bida' or at least makruh as they are Imams and what they do is a kind of mura-at (مراءاة) or Riya' (رِياء).
- Abu Hurairah (May Allah be pleased with him) reported: The Messenger of Allah (ﷺ) said, "A slave becomes nearest to his Rubb when he is in prostration. So increase supplications in prostrations."
[Sahih Muslim]
وعن أبي هريرة رضي الله عنه أن رسول الله صلى الله عليه وسلم قال: "أقرب ما يكون العبد من ربه وهو ساجد، فأكثروا الدعاء"
Narrated Abu Mas`ud Al-Ansari:
Once a man said to Allah's Messenger (ﷺ) "O Allah's Messenger (ﷺ)! I may not attend the (compulsory congregational) prayer because so and so (the Imam) prolongs the prayer when he leads us for it. The narrator added: "I never saw the Prophet (ﷺ) more furious in giving advice than he was on that day. The Prophet said, "O people! Some of you make others dislike good deeds (the prayers). So whoever leads the people in prayer should shorten it because among them there are the sick the weak and the needy (having some jobs to do).[Sahih al Bukhari]
حَدَّثَنَا مُحَمَّدُ بْنُ كَثِيرٍ، قَالَ أَخْبَرَنَا سُفْيَانُ، عَنِ ابْنِ أَبِي خَالِدٍ، عَنْ قَيْسِ بْنِ أَبِي حَازِمٍ، عَنْ أَبِي مَسْعُودٍ الأَنْصَارِيِّ، قَالَ قَالَ رَجُلٌ يَا رَسُولَ اللَّهِ، لاَ أَكَادُ أُدْرِكُ الصَّلاَةَ مِمَّا يُطَوِّلُ بِنَا فُلاَنٌ، فَمَا رَأَيْتُ النَّبِيَّ صلى الله عليه وسلم فِي مَوْعِظَةٍ أَشَدَّ غَضَبًا مِنْ يَوْمِئِذٍ فَقَالَ " أَيُّهَا النَّاسُ، إِنَّكُمْ مُنَفِّرُونَ، فَمَنْ صَلَّى بِالنَّاسِ فَلْيُخَفِّفْ، فَإِنَّ فِيهِمُ الْمَرِيضَ وَالضَّعِيفَ وَذَا الْحَاجَةِ ".
- Abu Huraira reported: The Messenger of Allah (ﷺ) said: When any one of you leads people in prayer, he must shorten it for among them are the weak, the infirm and those who have business to attend.
[Sahih Muslim]
وَحَدَّثَنَا حَرْمَلَةُ بْنُ يَحْيَى، أَخْبَرَنَا ابْنُ وَهْبٍ، قَالَ أَخْبَرَنِي يُونُسُ، عَنِ ابْنِ شِهَابٍ، قَالَ أَخْبَرَنِي أَبُو سَلَمَةَ بْنُ عَبْدِ الرَّحْمَنِ، أَنَّهُ سَمِعَ أَبَا هُرَيْرَةَ، يَقُولُ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِذَا صَلَّى أَحَدُكُمْ لِلنَّاسِ فَلْيُخَفِّفْ فَإِنَّ فِي النَّاسِ الضَّعِيفَ وَالسَّقِيمَ وَذَا الْحَاجَةِ " .
By the way most U'lama say the best is to extend/prolong the qiyam and neither the sujjud nor the ruku' and some said it's better to prolong the sujjud and ruku' for day prayers (during daylight) and to prolong the qiyam for night prayers! According to the following Hadith
Jabir reported Allah's Messenger (ﷺ) as saying: The most excellent prayer is that in which the duration of standing is longer.
[Sahih Muslim]
حَدَّثَنَا عَبْدُ بْنُ حُمَيْدٍ، أَخْبَرَنَا أَبُو عَاصِمٍ، أَخْبَرَنَا ابْنُ جُرَيْجٍ، أَخْبَرَنِي أَبُو الزُّبَيْرِ، عَنْ جَابِرٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " أَفْضَلُ الصَّلاَةِ طُولُ الْقُنُوتِ " .
This Hadith can also be found in Sunan Ibn Majah and Jami' at-Tirmidi