Time limit H1B petition renewal application can be filed

My H1B Petition(also visa) is approved(first) from Oct 2013 to Aug 2016. I would be moving to India in Feb-March 2016 due to some family reasons.

My questions is till when I/my employer is eligible to file for my H1B petition renewal so that I can come to US for project assignment again without going through the lottery process?

I am planning to be back in US after 2 years of stay in India however looking for information how feasible it is if I have a US project assignment ready at that time in my company.

You are cap-exempted for 6 years from the last day you held H-1 status i.e. 6 years from the day you leave US.