How often should a subscribing FeedSync application or service poll for Feed changes?
As in any polling system, the average latency that a user will experience to get a notification will be one-half of the polling interval. For some of the examples here, such as calendar synchronization, a polling interval of minutes is appropriate. For other use-cases, such as synchronizing a contact list or (perhaps) favorites list, a polling interval of hours is sufficient. The publishers can use the window attribute in the sx:sharing element to express the size of the window of change history kept by the publisher. Subscribers should poll at least this frequently.
