Having worked to get it, seems that there's no good reason not to renew.
But there seems to be two discussions going on here: renew (before expiration) and reinstate (after expiration). Let's separate them. I'll stick with renewal (before it expires).
Check out 61.197. Relatively painless. Can be done online from a number of providers.
The infamous "POI Renewal" used to be for 121 captains and used to be treated by some as an "acquaintance" renewal - we had a beer together so let's renew. I doubt it was really ever supposed to be that way. The reg was changed as part of the 1997 Part 61 rewrite. Here's what it says now:
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91.197(a) A person who holds a flight instructor certificate that has not expired may renew that certificate by -
(2) Presenting to an authorized FAA Flight Standards Inspector -
(ii) A record showing that, within the preceding 24 calendar months, the flight instructor has served as a company check pilot, chief flight instructor, company check airman, or flight instructor in a part 121 or part 135 operation, or in a position involving the regular evaluation of pilots
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It's that last part that remains of the old POI Renewal and applies to 135 as well as 121 pilots. Here's what FAA Order 8700.1, the GA Inspectors Handbook Vol 2, Chapter 11, Section 1(C) has to say about it (the reference to the "old" rule is the way the FAR provision read before the 1997 revision):
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Section 61.197(a)(2)(ii). Individuals have asked FAA about the intent of the statement, “. . . in a position involving the regular evaluation of pilots” in § 61.197(a)(2)(ii) and whether it has the same meaning as the old provision in § 61.197(b). The FAA rewrote § 61.197 to expand the renewal provisions, mainly to include other PICs. For example, the following PICs, who regularly evaluate pilots, have the same reward provisions as a PIC in a part 121 operation:
• A PIC of a multiple pilot flightcrew aircraft under part 135
• Corporate PICs of a multiple pilot flightcrew aircraft under part 125 or 133
• U.S. military pilots who are PICs of a multiple pilot flightcrew aircraft
• U.S. military instructor pilots and examiners who regularly evaluate pilots under part 125 or 133
• Flight instructors who actively instruct in part 61 schools
NOTE: FAA ASIs should review evidence of the applicant’s employment, which should clearly show that the applicant is in a position involving the regular evaluation of pilots. ASIs also should have personal knowledge of the applicant’s flight instructing capabilities and qualities before renewing that applicant’s flight instructor certificate.
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So the requirements for a "POI Renewal" are:
1. in a position that involves evaluation of pilots, such as captain of a multi-pilot crew
2. some record that shows what the pilot's position is and her evaluation duties
3. personal knowledge of the pilot's instructional capabilities.
No, it's not a POI can issues/reissue a CFI certifciate because he feels like it.