How many days can my SIM be inactive before being disconnected?

Hi Ifeanyi, An inactive/dormant line for 360 days without any chargeable activity will be terminated, recycled, and re-assign to a new user.

Dear Ifeanyi
Dormant/inactive lines, MTN will recycle prepaid lines after 360 days and Consumer lines after 540 days of inactivity (if the line is not used for any chargeable activity).
MTN also have a service called Keep My Number service which you can use to reserve the number.

MTN Keep My Number (KMN) is a special service that allows you to retain your numbers in the event that you travel out of the country or stay inactive/dormant for more than 360 days.
Kindly find the different plans below:
1 year plan cost N511.90k, to activate, dial *365*1# or text KMN1 to 36500
2 years plan cost N819.05k, to activate, dial *365*2# or text KMN2 to 36500
3 years plan cost N1,228.57k, to activate, dial *365*3# or text KMN3 to 36500