A number on GSM LTE might be disconnected automatically 30 days after service expiry/cancellation. On Warp 5G (Previously Super LTE), a number will be disconnected at the conclusion of 50 days post service expiry/cancellation. After that period, numbers will be put back into recirculation.
You can ‘Snooze’ your line to keep it in service to avoid the risk of losing the number. This involves setting up the AutoPay without any plans, thus letting the line be renewed automatically every 30 days with just the monthly service fee and taxes.