Your eVisa is valid for 3 months once it has been approved and must be valid for your entire stay in the country. As long as you can enter and exit Egypt before that expiry date, you'll be able to visit.
If your eVisa is expired, however, and you’d like to enter Egypt after the expiry date, you’ll need to apply for another one. Feel free to reach out to us, and we’ll help you figure out your next steps.