If you’re a collector, keep good records so you know your basis for each item.
For example, say you bought a painting for $6,000 and you hold it until death, when it’s worth $20,000. Your heirs can sell it for $20,000 and owe no capital gains tax. (The full value will be included in your taxable estate, though.) Thus, if you inherit collectibles from anyone, you should have them appraised right away, to establish a new basis, for all the reasons mentioned above.
On the other hand, when collectibles are given away their original basis goes with them. If you give that $6,000 painting to your son, for example, his basis will be $6,000 and he’ll owe tax on a $14,000 gain, if he sells it for $20,000. Again, if you’re given collectibles, find out what the giver’s basis was and collect documentation, if it’s available.