For most entry level jobs (CFI) and all 121 SIC jobs you only need a 2C. Most of us, when not serving as a 121 PIC, will get a 1C, allow it to lapse to a 2C at six months, and then renew the 1C at one year. Don't need to drop the coin every six months just to go to work.

But if you're actively applying to airline jobs (regional or major) you should maintain a current 1C because that's one of their application requirements. So every six months in that case.

Also need a passport for airlines, with > six months until expiration.