In episode 183 of Semantic Mastery's weekly Hump Day Hangouts, one participant asked whether it is possible to revive inactive YouTube channels that are still ranking in SERPs.
The exact question was:
What has been your experience if any with youtube channels that have been inactive for some time but are still in the SERPs and some on first few pages. I am wanting to revive them if you think that is possible. Started out with 40-50 embeds for the specific ones I wanted to move up in ranking.