It would depend in the video actually (and how many are all talking at once ><). But at most (as in, really taking my time ><), for a 20 min video, it would take me 3 days to time. (In reality, whenever I have the time I rather do the entire vid all at once, so... 3 hs maybe?).
After the 23rd I still have lessons to attend to, but I would de able to set apart at least one, maybe two hours a day to time ^^ (and don't worry, I'm always happy to help, so you're not imposing at all! I'll tell you if things start to get too much for me to handle ^^ )