The BACnet Device plugin has a hard-coded SUBSCRIPTION_LIFETIME constant of 120s that forces all COV subscriptions to time-out after 2 minutes, causing SolarNode to then re-subscribe, causing all subscriptions to generate a new "datum created" event, even if the property has not changed.

For polling-only datum collection this isn't much of an issue, but for event-based collection the subscription lifetime should be configurable, so it can be set to something reasonable for the site. Expose a setting for this, so users can configure it.