Don't worry. you will have plenty of time. They haven't rolled out this feature to all players so it wouldn't be fair for TL to make it limited. Even after they finish rolling it out to everyone, they will have to give all players a decent amount of time to earn it. It will be yonks before they take Platinum away. I do hope they do roll this out to everyone soon. I'm at 173 ingots, and I think i'll have to stop evolving my dragons when I finish earning Platinum. I have too many dragons at epic already so I will be running short on evolution opportunities.