Expiry is not a soft warning. On every one of these products the balance is tied to the term, and the provider terms say what happens once the term passes.
What the providers state
- Boost states the prepaid SIM is automatically deactivated six months after the expiry date of the last recharge.
- Boost states that to keep your number you must keep your service recharged or transfer to another provider.
- The Optus prepaid data only plan states you must recharge within six months of your data allowance expiring to keep the service active.
Why the number is the real casualty
Data can be replaced by buying more. A number cannot. If the service is allowed to lapse for long enough, the number is no longer yours to keep, and reactivation is no longer guaranteed.
How to avoid the whole scenario
Turn on auto recharge. Boost states auto recharge is available if you have registered a valid credit or debit card, which removes the single most common way prepaid services die.
What we could not verify. Where a provider has not published a figure we mark it unknown rather than estimate it. Re-read the provider page linked below on the day you decide.