Visitor visa for father in law

[Cognizant]

Hi everyone,

I am applying for visitor visa for my father in law next month. I am sponsoring. I have couple questions.

1. How recent should be my employment letter? Is two months recent letter sufficient?

2. I have applied visitor visa for my parents on Aug 23 and they got their visa approved. So, is it ok to send my Father in law with 1 month gap?

I really appreciate your replies and thanks in advance.

Cognizant.