Even without speedrunning
The lovely chaps at GameXplain did everyone a favor and played Mighty No. 9so we don’t have to, and they uploaded the entire credits roll that lasts just over 3 hours and 48 minutes. The excessive length is thanks in part to thelisting of over 67,000 Kickstarter backers, most of whom are only listed as “Mighty No. XXXXX – A Generous Backer” for one reason or another.
I’ve heard the average time to clear the game is between three to five hours, though it has already been completed in around an hour by speedrunners. Personally, it took me just over five hours thanks to cheap bosses and their one-hit kills; five precious hours I’ll never get back.