Why you should not allow your domain to expire
When your domain expires, a quick Whois lookup will reveal that the domain was updated a day after the domain was meant to expire and the new expiry date would be in the future, and the nameservers are changed. Do not be alarmed, the nameservers will automatically revert back when the registration/renewal fee is paid.)
You have between 28-28 days to pay for your domain name and keep it (at regular price). After this period, it will cost extra to renew N51,000, and you risk losing the domain to another buyer.
This applies to non .ng domains only.
If a domain is renewed later than the expiry date, once the domain is renewed, it starts counting from the previously expired date. This applies for both .ng and non .ng domains.