Meaning #2: something that has been in a family for generations

As a practical matter, for something to be handed down between generations
it must both survive multiple generations and appeal to multiple
generations.

Therefore, by corrolary, an heirloom but be of high quality, and have
aesthetic appeal which is able to transcend periodic trends. To me that
generally means classic design elements.

To the OP, I often leave a little wane on the underside of a tabelop
glue-up. It doesn't bother me and I doubt that it will be a consideration
for my ancestors.

-Steve