my device activation will lost after one month, i find that the deivice activation redis key will expire about one month, but i dont set any expire config( like that device_session_ttl), how to resolve it and this is why, i feel so confused , thanks
If you don’t set it, it will fallback to the default value of one month.
well, i dont want to lose the activation and save it forever, how to set it（or its activation must out of date for a fixed date）? thanks for your reply, brocaar:grinning:.
if i active the device and send the device heart to my server within device_session_ttl, the activation will always exist, please reply my two question, thanks brocaar. 
AFAIK yes, if the device sends a message within device_session_ttl, it will stay activated.
thanks , i try that, it will reset the device_session_ttl 