When you get closer to renewal time, you don't need to update your mileage.
Even if your app says you have 0% left, we don't ask you to pay for more mileage in the last two months of your policy. You can still drive and your policy is still valid.
However, you do need to think about whether you'll need more mileage when you renew. Once you've had your renewal invite in the app, just start a chat to make any changes to your renewal, including declared mileage. Adjusting your mileage allowance at renewal could change the price. Once a member of the team makes any requested changes, you'll be able to see the new renewal quote in the app, before confirming you want to go ahead.