Was it a mistake getting veneers at 19? Very depressed

Veneers done well will last 15 years plus. They appeared in the literature in the early 80's and so have not been around for 50 years yet. I have been placing them since 1988 and I have some that are still in place at 30 years. The only change is the esthetics but functionally they are still stuck. The patient's gumline and wear are the main changes. 
Be prudent with your hygiene and enjoy them. They are a good investment if it improved your appearance and made you feel confident!
Best regards,
Dr. Ed Lowe

Your veneers were done, you love the look, take care of your investment by going back to your dentist regularly and you'll be fine.  Forget all those could've, should've, and would'ves.  Enjoy your new smile and take care of them by brushing and flossing.  Veneers have shown to last over 20 years.  Your may last 2 years or 50 years if you take good care of them.  

Hi:At this time my recommnendation is to enjoy your new teeth and not to worry about replacement. Make sure you floss, brush and get regular cleanings.Best,Dr. Maddahi

If your enamel was weak, it may have been the best idea to cover and protect your teeth. If your doctor did minimal prep veneers, there will be plenty of tooth if they ever need to be redone. You're right in saying each time they're replaced you may lose a little more tooth structure, but we're talking 0.1mm. With veneers, if there is no cavity, very little of the tooth is removed. As little as possible. Take care of what you have now to extend the life of your veneers. It may be 30 years before you look at replacing them. If you're happy with the result of the veneers today, just make sure you get regular check ups with your dentist and take good care of the veneers to protect them.