Your eVisa is valid for 60 days once it has been approved. As long as you can enter Laos between the "date of approval" and the "valid until" date stated on your eVisa document, you’ll be able to visit.
If your eVisa is expired, however, and you’d like to enter Laos after the expiry date, you’ll need to apply for another eVisa. Feel free to reach out to us, and we’ll help you figure out your next steps.