How many times can you replace a crown? Will the tooth underneath be strong enough? (Photo)

My front four teeth have recently had root canals and all porcelain crowns placed on .Whilst they look better than when the accident happened there’s a few things I would like changing with them.(whitening, gum sculpting and getting rid of the slant they currently have) I am only 25 so have accepted I will need to get my crowns redone a couple of times in my life. My only concern is whether the tooth underneath will be strong enough for this? I really want to avoid implants/bridges.