A small surah recited with tarteel and qira-ah, can take the same time as it takes to recite a longer surah (if recited in an ordinary manner). Sayyidina Rasulullah Sallallahu 'Alayhi Wasallam recited the Qur-aan with calmness and little by little. He did not recite with haste. The time it took him to recite a small surah, takes another person the same time to recite a long surah. The reason his feet swelled, was due to standing for long periods.