> ## Documentation Index
> Fetch the complete documentation index at: https://docs.debridge.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Refreshing Estimates

> How and when the estimates should be refreshed.

## Transaction Submission Timing

It is recommended that transactions returned by the `create-tx` API be signed and submitted within **30 seconds**. When `response.tx` is submitted
within this window, the likelihood of successful order execution exceeds **99.9%**.

There is no explicit time-to-live (TTL) on the transaction itself — i.e., the period between receiving the `create-tx` response and submitting it
on-chain. Transactions may remain valid for extended periods, especially when no [pre-order-swap](/dln-details/dln-specifics/bridging-non-reserve-assets) is
involved or the [pre-order-swap](/dln-details/dln-specifics/bridging-non-reserve-assets) is between stablecoins.

***

## Handling Operating Expense Fluctuations

When the `prependOperatingExpenses` [parameter](/dln-details/integration-guidelines/order-creation/creating-order/api-parameters/api-parameters) is
enabled, special attention must be paid to how token approval amounts are set.

If the allowance **exactly matches** `response.estimation.srcChainTokenIn.amount` and there's a delay — typically more than a minute — before
submitting `response.tx`, operating expenses may increase. In that case the estimate should be refreshed. If the updated expense exceeds the approved
amount, an additional approval step is required, degrading the experience.

### Recommendation

* **Set token allowance to infinity** if user experience allows
* **Or** add a 30% buffer when setting the allowance to absorb changes

```ts theme={null}
const { approximateOperatingExpense } = response.estimation.srcChainTokenIn;
const approveAmount = srcChainTokenInAmount + approximateOperatingExpense * 1.3;
```

This ensures the approved amount remains sufficient even if gas costs or execution fees rise before submission.

***

You can find more examples in the [code reference](https://github.com/debridge-finance/api-integrator-example/tree/master/src/scripts/orders)