In all seriousness though, how many people are really going to consider a t-shirt to be a family heirloom, that you _should_ pass down through the generations?
The handme downs are passed down through each generation of siblings, but unless you have space, or clothes are adult sized its probably gonna be donated.
Not the parent, but I have many t-shirts that are well over 10 years old. Some of them I wear regularly. A good quality fabric can definitely last decades, we're just getting unused to that and assume everything has to break down.
Im mid 20s, and I can still have tshirts from over 10 years ago. Rotate through them everday, in my experience brandname 10-20 dollar shirts, or kirkland 3 dollar shirts have held up.