I'll eventually have to get my 2nd class done when I get my CFI checkride lined up
Why?
61.23 Medical certificates: Requirement and duration.
(a) Operations requiring a medical certificate. Except as provided in paragraphs (b) and (c) of this section, a person—
(1) Must hold a first-class medical certificate:
(i) When exercising the pilot-in-command privileges of an airline transport pilot certificate;
(ii) When exercising the second-in-command privileges of an airline transport pilot certificate in a flag or supplemental operation in part 121 of this chapter that requires three or more pilots; or
(iii) When serving as a required pilot flightcrew member in an operation conducted under part 121 of this chapter if the pilot has reached his or her 60th birthday.
(2) Must hold at least a second class medical certificate when exercising:
(i) Second-in-command privileges of an airline transport pilot certificate in part 121 of this chapter (other than operations specified in paragraph (a)(1)(ii) of this section); or
(ii) Privileges of a commercial pilot certificate; or
(3) Must hold at least a third-class medical certificate—
(i) When exercising the privileges of a private pilot certificate;
(ii) When exercising the privileges of a recreational pilot certificate;
(iii) When exercising the privileges of a student pilot certificate;
(iv) When exercising the privileges of a flight instructor certificate and acting as the pilot in command;
(v) When exercising the privileges of a flight instructor certificate and serving as a required pilot flight crewmember;
(vi) When taking a practical test in an aircraft for a recreational pilot, private pilot, commercial pilot, or airline transport pilot certificate, or for a flight instructor certificate; or
(vii) When performing the duties as an Examiner in an aircraft when administering a practical test or proficiency check for an airman certificate, rating, or authorization.