Tier 2 Sponsor Visa Validity requirements for Parents

[kumarp]

Dear Guru's,

This is my first post, I have below questions please clarify me.

I want to apply visit visa to my parents I am on Tier2 visa, the issue is my visa validity is till April 30 2017. I want to bring them in March. Is there any requirement which states as a Sponsor do I need minimum of 6 months visa validity??

If I want to apply extension before my visa expires, how many month before I can go for extension ? If i go early dose they give only 2 yrs visa or 3 yrs visa (bcz if they give 2 yrs my 5 yrs not complete for ILR) or another extension i have to go for? ( My employer will give COS for 2 yrs or 3 yrs... what ever i request)
Thank you very much....