To keep your line active, just ensure there’s usage, reload or purchase any add-ons within 90 days from last purchased date. Your Unifi Mobile line will be terminated after 90 days if you do not buy any add-ons within 90 days.

You cannot check your account expiry from app, customer service currently, but you will receive sim expiry message on every 30,60 days.

forumer update:
-Using any freebies from add-on data/call/sms will not extend your validity
Using any data/call/sms from your purchased add on will not extend your validity

Official Statement:
Use any usage from add on will extend the validity

but you will receive sim expiry message on every 30,60 days.

Regards to the validity. No one could answer you because the time has not reached. we will know the answer on April 21