One i buy a theme, i can use it forever? or in a year i have to buy it again?

Yes you can use it forever hope there will be no problem at all.even you will received 6month support.
Standard license is enough for that.

One more thing the license will be valid for lifetime but you will be able to use the theme only for a single end product (as like for a single domian).

Thanks a lot guys! :wink: