Zirconia crowns are very strong and durable. Can be replaced if needed, but with some difficulty. But since u said aesthetic need, needs a proper smile analysis done before u start any treatment and the present condition needs to be assessed. May be some teeth require RCTs. Advisable to get RCTs done before placement of zirconia crowns.  15 years is good enough period, there will be bone remodeling happening with age which may demand replacement of caps at later stage. If u maintain your hygeine well with regular dental visits, the caps remain durable for even more.