"If you work hard to get a license for something never let it go." Heard that once years ago and it stuck with me.
I "graduated" from flight instructing in 1989 and still keep a current CFI with the help of AOPA's CFI online renewal program every 2 years.
At 51 years old and 12,000 hours in the books I don't see going back to CFIing even in the worst of times but still can't let it go.
In practical terms I am so out of touch with light aircraft GA ops and all things associated that have changed over 25 years that I would probably make a poor initial instructor anyway. Been flying jets since and probably have logged a grand total of 30 hours SEL since 1990 although I have been a company instructor and FAR 135 check pilot in jets and certainly my CFI certificate and experience helped me during that point in my career.
A 2 year CFI renewal program (in the US) is only $120 and can be done online. Keep your CFI current.