Best Practice for addon MQTT discovery sensors

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