Hi, I’m very very sorry for this very very late reply. I had missed the question. Just in case this is still interesting to someone…
There is no hard limit as far as I can tell, but the limit is on how powerful your server is, how long the RSS feeds (as in number of episodes, probably how heavy the images?), and how often you pull.
RSS polling still sends sidekiq to the roof, some feeds may take 20 minutes and more to process, and if you 5 simultaneous jobs as clog by these long RSS pulls then the job queue starts to grow. The real limit is when Sidekiq doesn’t have enough time to process all jobs in all queues between RSS polls. When that happens then the next RSS poll is likely to clog the queues further and eventually something will crash/restart. The user might not notice anything. Some RSS feeds might not be updated because of this.