How long can I expect my Durathin veneers to last?

The space between the two is too large. The teeth to fill the space would make the teeth look very wide/chiclet like. I think a combination of Invisalign and bonding veneers would work.

It all depends on how much composite you have on the front teeth.  A conservative option would be to do whitening and just replace the bonding with a lighter shade.  Another option could be to consider a minimal prep veneer to cover the front of the tooth to get a more long lasting...

Hello,These stains on your teeth are mostly caused by excessive fluoride. Teeth whitening could make it worse. For a permanent solution, you might consider getting laminate veneers.