Are closed markets auto-removed from the Stream API subscription?

When you first subscribe, a validation for the number of requested market on the subscription is performed. If that exceeds the number of allowed markets then an error code SUBSCRIPTION_LIMIT_EXCEEDED is sent on subscription.

On re-subscribe this validation is run again and excludes any closed markets. To remove closed markets from subscription cache the Stream API runs an scheduled internal job to evict closed markets from the cache (every 5 mins) and a market is marketed for deletion after 1h of being closed. If a market is closed it needs to be deleted from the cache with above procedure to be excluded from the count.