myki "credit" does NOT expire after 90 days.

So I'm perfectly happy to criticise myki when they get it wrong (which they seem to be doing an awful lot of), but I'll also defend them when other idiots put out incorrect information about them.

This has been in the news before, but good old Auntie has dredged it up again:

Myki authority 'reconsidering' credit expiry rule: PTV

It would appear nobody in that story has their facts straight, including the new head of Public Transport Victoria Ian Dobbs, who it would appear knows next to nothing about one of the major things he's meant to be looking after (or has been horrendously misquoted, which is is equally as likely).

To cut a long story short:  myki credit, or myki money to use the correct time, does NOT expire.

If you top-up your myki at a vending machine, or retailer like 7/11, or even online on the website, the credit does NOT expire.  I'm capitalising NOT every time because some people just don't appear to get it.

Where the 90 days comes into this, is if you choose to do an online top-up.  Let's examine the series of events.

1. you apply for an online top-up on the myki website
2. the details of your top-up get sent to every single myki reader and myki vending machine on the network.  These details, along with the details of every single other outstanding online topup (which could number many thousands of people quite possibly) go in a file called an "action list" (not that you need to know that).  It's just a big long list of myki card numbers, amount of myki money to be topped up, and also details of any myki pass to be topped up.
3. when you touch your card to a reader or myki machine (after the top-up details have arrived at that reader or device) the details of the top-up are written to your card (kind of like writing a file to USB stick.  And someone would argue, almost as fast.)
4. the fact you have "collected" your top-up is sent back to the myki computer and your topup details are then removed from the list.  The next time the list is sent out to all the myki readers and machines, your top-up details won't be in the list any more.

However.  Let's say you apply for a top-up to your myki card.  But you don't use it, at all.  You leave it sitting in your drawer, or wallet, or whatever, because you don't use public transport very often.

For 90 days, your top-up details sit in the list on every single myki reader and machine around Victoria (well, that's the theory).

After 90 days, your top-up is removed from the list.  It apparently gets "archived".

Note:  Any balance on your card is unaffected by this.  So, say you had $10 on your card... and you did an online top-up of $20.  Myki owes you $30 of travel.  

After 90 days the $20 top-up gets archived.  Then, say a few weeks later, you finally decided to go for a trip on the train.

When you touch on, the reader sends a signal back to base saying "they've decided to travel!  Quick, if there's an archived top-up, send it out so they can collect it!"

So at this point, your top-up is re-added to the action list.  This can take a while... up to 24 hours, but I've had it happen the same day, see here:

That's the travel history from a myki card I hadn't used for about 6 months.  At some point I got a reimbursement credit back (for an overcharge, of course).  This is essentially the same thing as an online top-up, except initiated by myki and not you.

In this case I topped up and travelled in the morning.  Then, later on in the day when I touched on again, the reimbursement appeared.  I actually did this on purpose because I wanted to test how this 90 day thing might work, and yes it did.

So as you can see, your credit does NOT expire.

Yes, if you don't use your card for more than 90 days, you may have to top up some other way to use the card.  But you will get your money, and more than likely the same day.