How long can you drink green tea before you build up an immunity to it in helping your metabolism?

I heard that you should drink it for so many days and get off for a while, but I don't know what the amount days is for drinking green tea and the amount of days to be off it. If someone can help me with the ratio, I would greatly appreciate it.

Also any more tips for keeping the metabolism raved up will be appreciated.

Thanks in advance.