Can you lengthen veneers without having to replace the entire veneer?

Hello Lex,It is not possible to extend your veneers with any material that will last or be the slightest bit reliable.  I would recommend replacing the veneers that are too short.  The price would not generally be less because the dentist would have to replace the entire veneer.  I know it seems like paying double for the same veneers, but I suspect that the enhancement to your appearance and self-confidence will be much more valuable than the cost of replacement.  Good luck and I hope this helps. I'm an expert on veneers, so follow me if you have more questions.Sarah Thompson, DMDSoft Touch Dentistry

Porcelain is made under extreme heat.  Unfortunately, the only way to add porcelain to your veneers is to put them in a porcelain furnace (obv, not possible).   Trying to add bonding to them will not work long term.  So unfortunately you're only option is re-doing them. 

It depends what your veneers were made of.  Porcelain which I feel is the best choice cosmetically, can not be added to.  If you had them done in high school and were able to file them down yourself, it is possible that they were done with composite resin.  If they are composite, that could be added to provided the rest of the material is in good condition.  At this point, if you are a perfectionist, it may be best to start over with porcelain if your budget allows.  Good luck!