Gems / wark blessings in War

How many wars must a player fully participate in before they are entitled to receive the gems / war blessings?

I know if someone joins in the first or second war (of the four) then they are entitled to the gems / war blessings.

At what point does this stop?

You have to be in an alliance for at least the last two wars. 

Thanks. I thoughts as much but couldn’t work out how to search this site to find that answer.

I think it’s 7 days, so you have to have joined before the end of the penultimate war…