Does it sound natural? If not, correct it

[NewHopeR]

(The following is not written by me but someone else)

To satisfy your humble request and your sincerity in getting your mistakes or flawed usages corrected, I am more than happy to be your English teacher for once as long as your humble appearance does not expire. now it is my turn to have a better feeling.

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I'm not sure whether "your humble appearance does not expire" is natural English, or not.

 

[Route21]

As an NES but not a teacher, whether or not any of the quoted text is grammatically correct, I would not consider it to represent "natural" Englsh.

Regards
R21

 

[5jj]

I agree with R21.

"your humble appearance does not expire" is meaningless.