Could it be too early to get crowns at age of 17?

Not if you need them: Ideally, individuals should never need crowns. Crown are necessary in certain cases such as traumatic injuries to teeth as well as extensive caries (dental decay) where there is too much tooth structure lost to rely on fillings alone to hold and\or stand the test of time. When one requires a crown, it should be done, whether you are 70 or 17. If it's for cosmetic reasons, discuss all options first.

No: No, it's not too early.