Best Practice for addon MQTT discovery sensors

Third party integrations
1

I’m developing an addon which reads external hardware for its own purposes and to forward to Home Assistant via MQTT discovery.

  1. What is a ‘good’ update interval for HA?
    Hardware reads are every 15 seconds.
    Is this too rapid for HA?
    Should I only publish to HA every 30 seconds, 60 seconds…
  2. How to handle bad data from the hardware?
    When the addon gets bad data should it:
    take the MQTT sensor offline (availability topic = ‘offline’),
    leave online and set the value (state topic) to ‘unknown’
    leave online but not publish and let HA timeout after ‘exp_aft’ seconds
    and/or something else?

Thanks
Mike