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28 day vs 30 day expiry: Why it matters


Some mobile providers are shifting to prepaid plans with 28-day expiry. How much more will you pay as a result, and might you actually be better off?

amaysim recently made headlines by changing its UNLIMITED mobile deals and significantly upping the data quota on each plan. Its most popular plan, UNLIMITED 5GB, is changing to UNLIMITED 7GB gaining an extra 2GB of data.

On the surface, that seems like a win for consumers, except at the same time amaysim also altered the expiry time of each of those plans down from 30 days to 28 days.

amaysim is hardly alone in this respect; many providers have plans with 28-day expiry periods rather than 30 days. Some providers keep matters rather vague by referring to a "month" of subscription to prepaid services, but if you dig deep enough most still think of a month as being a 30-day span. If they switch to a 28-day deal, that means you do rather better in February but slightly worse in January, March, May, July, August, October and December. Plans which have a 28-day expiry include Telstra's Freedom, Optus My Prepaid Ultimate and Vodafone's Combo plans.

So what’s the problem with a 28-day expiry period versus a 30-day one, aside from the rather obvious fact that you’re getting two less days?

The big issue how many times you need to recharge over a year or longer. Mobile number portability means it's easy to switch carriers, but the reality is that most of us are rather lazy, and tend to stick to our existing plan rather than seeking out new deals. That means anyone jumping onto a 28-day plan will probably use that plan for longer than a single recharge period.

Let’s use some mathematical examples to show how this plays out over a year’s worth of recharges for a fictional provider with a $20/month plan that switches from 30 days of expiry to 28 days without altering the plan cost. The following table shows how much you’ll pay over a year when these switches are made.

Fictional Telco Plans30-day expiry28-day expiry
Cost of recharge$20$20
Number of recharges in a year (365 days divided by Expiry)12.1666666713.03571429
Total yearly cost$243.33$260.71

As you can see, the loss of two days in each recharge period adds up over a year to nearly as much as the cost of a full additional recharge; this would apply whether you were paying $20 per month or any other sum.

Count data per day, not number of days

That isn’t to say that a 28 day plan is automatically a "bad" choice. You have to weigh that shorter expiry period against the inclusions on the plans. With most plans in Australia now offering unlimited calls and texts to Australian numbers, data is going to be the main battleground, and the most useful measure is how much data you can use each day on the plan.

For instance, the old amaysim UNLIMITED 5GB plan offered an average of 166MB per day (5000MB divided by 30). The updated 7GB plan offers 250MB per day, so you're actually getting more data for your money. Here's how much data per day you get with a number of plans all costing around $40 a month and offering unlimited calls:

Optus My Prepaid Ultimate4GB28 days$40.00Optus 4G
Telstra Freedom Plus3GB28 days$40.00Telstra 4G
Vodafone Combo4GB28 days$40.00Vodafone 4G
amaysim UNLIMITED7GB28 days$39.90Optus 4G
Kogan 5XL5GB30 days$36.90Vodafone 3G
TPG T4G III5GB30 days$39.99Vodafone 4G
Boost UNLTD3GB30 days$40.00Telstra 4G
Vaya Unlimited XL7GB30 days$34.00Optus 4G

You can check the full details of competing plans, including their expiry periods, with our Mobile Phone Finder to find the plan that best suits your needs. We've pre-populated the table below for a moderate-use prepaid plan, but you can adjust to suit your particular needs by clicking on "Filter Results" to change the data or call inclusions:

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4 Responses

    Default Gravatar
    MerranSeptember 8, 2017

    I have $40 per month Telstra Freedom Plus plan. Telstra salesman says I can save $200 per year by changing to $50 BYO postpaid plan. I use my mobile as a hot spot for my laptop, but generally consider myself a frugal user. Can I save by changing to post paid?

      JoanneSeptember 8, 2017Finder

      Hi Merran,

      Thanks for reaching out to Finder.

      Generally, when choosing between prepaid vs postpaid plans, there are two main questions to answer. Do you need a new phone? If you want a new handset on a plan, postpaid is your only option. Alternatively, buy the handset outright and pair it with any type of plan.
      Are you worried about excess fees? If you want control over exactly how much you spend per month, prepaid is your best bet.

      I would recommend you to assess the benefits and compare them side by side and see what would best suit your needs. Our article on Telstra’s Freedom Plus prepaid goes unlimited might be able to provide further details to your enquiry.


    Default Gravatar
    HenryMay 15, 2017

    In a mobile phone plans that states the repayment cost included in the $120 monthly for the phone is $20 per month. The contract period is 24 month. When I multiply 24 month times $20 I will have paid $480 during the 24 month.
    As the phone cost is $1000 do I have to pay the balance of $520 on the end of the contract to make the phone my property.

      Default Gravatar
      ArnoldMay 16, 2017

      Hi Henry,

      Thanks for your inquiry.

      No, you don’t have to. Your Handset Repayments are a way for you to pay the cost of the handset over 12 or 24 months, rather than paying a large upfront fee.
      If your device is paid off, you now have ownership of the handset, you’ll no longer be charged handset repayments and therefore won’t receive any device credits.

      Hope this information helped.


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