Yes, it’s that urgent and important.
We have updated our software to increase security for our users. Our new software requires new wallet addresses.
Right now, all your addresses work just fine. But after September 30, you won’t receive coins that were sent to the old addresses.
So, please check all the websites where you left the address for depositing purposes - mining pools, your business pages, you name it.
If you are expecting XMR to arrive in your wallet, make sure you use the new XMR address.