When an exchange fails, customers usually become unsecured creditors in a bankruptcy process. Your crypto is treated as a claim, not as property you control.
Collapsed platforms have shown that customer funds can be frozen for years and recovered only partially, if at all. When you hold on an exchange, you trust it to stay solvent.
If you do not hold the private keys, you do not actually control the asset. The exchange does, and its problems become your problems.
Withdraw long-term holdings to a hardware wallet where you control the keys. Keep only what you actively trade on the exchange.
Exchanges are useful for buying and trading, but they are not a safe place to store wealth. Self-custody is the only way to truly own your crypto.