100% worth it
Yeah so first to repair it you have to spend some gold / foods / runes / do some pvp battle if I remember correctly
Then you get the temple without star. The activation cost is 7.2M EVERY TIME, regardless of the number of star you have. Without starts, you get 20% less time for breeding
To get your first star, you need to activate it 3 times. So the first 3 times you'll have only 20% less time for breeding, and after the 3rd time, you'll get your first star. Which means, the next time you'll activate, you'll have 40% less time for breeding.
So just remember that whatever your number of star is or number of activation between star is, you have to pay 7.2 millions, it'll work for 2 days then you'll have to wait 3 days to activate again :)