Your cart expiration length determines how long customers (and Figure admin users) have to complete an order before the inventory is removed from the order.
You should select a length that provides enough cushion of time for people to comfortably add credit cards, addresses, order notes etc. 15 minutes is a decent recommendation.
The tradeoff is that while inventory is in someone's cart, it isn't available to others. So if the expiration length is too high, then that could create issues as well.
1. Click on Settings
2. Click on Carts
3. Set the "Cart Expiration Length" to your desired time in seconds
If you want your carts to reset after a certain length of time, add the number of SECONDS
to the cell for "Cart Expiration Length". For example, 900 seconds = 15 minutes.