H1B extension after going back to India.

I have my H1b which is valid till Oct/2016. I might have to leave to India by Dec 2015, can I apply for H1b again if I want to come back after my current visa expires. Will it be cap exmpeted and if yes till what time I can apply?

You can get a new h1 filed by a US employer and such petition doesnt require to be in the H1 cap, if you have not used your H1 for full 6 years

Can I apply at any time? or there is any time frame

You can apply at any time.