What Happens to Veneers/Lumineers After 10-15 Years?

While nothing lasts forever, the reasons for replacement can vary dramatically.  Most often, the reason is a color upgrade or surface "glossiness" re-do.  Loss of teeth is usually NOT the reason for "failure" 15-20 years later.

Since veneer preparations are very conservative, tooth structure still remains.  THIS can decay if not cared for, which could lead to a re-do of the veneer.

At age 25, I would say to expect to have the smile redone 2-3 times.  People are living longer, so one should expect to replace or maintain their case.

Most of our cases that are 25 years old or older are being done for no other reason than they want "whiter" teeth, but the teeth are otherwise completely healthy...

veneers are the same as natural teeth, if you will take care of them, they will stay life long. Choose good material and VERY GOOD COSMETIC DENTIST.

When a veneer has come near to the end of it's life cycle, it's pretty easy to replace.  Think about when you need new tires on your car.....you simply replace them.   Terrible analogy but basically the veneers are removed carefully.  New impressions are taken and then new veneers are made and bonded on.  The clock starts over now.  Technically there is NO limit to the number of veneers you could get on a tooth.  So don't worry about replacement.