What is the duration of these inner line permits?

What is the duration of these inner line permits?

Normally the permits are issued for a duration of fifteen days for the specific purpose of tourism only. Once in Sikkim these permits can be further extended for 30 more days in two spells of 15 days each. These extensions are granted only at Gangtok by State Home Department. Extensions beyond the period of forty-five days are vary rarely given. Foreigners who wish to stay in Sikkim for purposes other than tourism for longer period of time are required to apply directly to the to Ministry of Home Affairs, New Delhi. Extension of Inner Line Permit beyond 30 days can be obtained from the Foreigner’s Registration Office at Gangtok and Superintendent of Police at Namchi, South, Mangan, North, and Gyalshing, West for further period of 30 days.