You will need to gain 1000 subscribers in total and 4000 watch hours in the past 12 months, these are the two requirements for the YouTube Partner Program. The watch hours or the subscriber count won't be reset.
Replying to @TeamYouTube
To clarify, once you reach that threshold, do you remain a partner even if you have a bad year? Or must you always have 4000 watch hours every year to remain a partner?
2:45 PM - 24 Feb 2018
0 replies
0 retweets
1 like
Loading seems to be taking a while.
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.