First, the good news is that your porcelain veneers won't just "expire". They can last decades. Typically if something wears out, most commonly it's one veneer, not the whole set.
It may be necessary to replace veneers for a few main reasons:
A cavity forms around the edge where the veneer meets the tooth
The bonding adhesive is exposed and deteriorates, causing a veneer to "pop off"
Trauma or an injury breaks a large piece of the porcelain off
The replacement procedure doesn't have to be lengthy. If its just one veneer with an issue, that's fairly straightforward. In that situation where you are matching only one front tooth, you will wait to choose an experienced cosmetic dentist, because his communication and choice of a dental lab makes all the difference.
The cost isn't necessarily more expensive in and of itself, like the cost of everything else in life, the cost of cosmetic dentistry typically goes up over time. If it's ten years later, the cost will be significantly higher than the original cost.
Don't be afraid to get veneers because you are worried about having to replace them later. I have seen patient's lives changed because of their new smile, don't underestimate the power of a beautiful, confident smile. Also, I have seen my patients who have cosmetic dentistry become great at caring for their teeth. This makes everything last longer.
Veneers can last a long time. If you need maintenance, it can be managed easily by an experienced cosmetic dentist. Thanks for your question, Dr. Scott Greenhalgh, DDS