فَإِنْ كَانَ مُقِيمًا مَسَحَ يَوْمًا وَلَيْلَةً، وَإِنْ كَانَ مُسَافِرًا مَسَحَ ثَلَاثَةَ أَيَّامٍ وَلَيَالِيَهَا. وَابْتِدَاؤُهَا عَقِبَ الْحَدَثِ.
Meaning: A resident may wipe for one day and one night, while a traveller may wipe for three days and nights; the period begins after the occurrence of minor impurity.
A resident has 24 hours and a traveller 72 hours. The clock starts when minor impurity first occurs after wearing the khuffs, not when they were put on.
The duration belongs to the concession as a whole; it is not restarted with each prayer or each new wudu.