The Messenger of Allah ﷺ did not fast throughout any month except during ramadan. And when he observed fast (he fasted so continuously) that one would say that he would not break (them) and when he Abandoned, he abandoned (so continuously) that one would say: By Allah, perhaps he would never fast. (Using translation from Muslim 1157a)  

مَا صَامَ النَّبِيُّ ﷺ شَهْرًا كَامِلًا غَيْرَ رَمَضَانَ وَإِنْ كَانَ لَيَصُومُ إِذَا صَامَ حَتَّى يَقُولَ الْقَائِلُ لَا وَاللَّهِ لَا يُفْطِرُ وَيُفْطِرُ إِذَا أَفْطَرَ حَتَّى يَقُولَ الْقَائِلُ لَا وَاللَّهِ لَا يَصُومُ