If you have bought an altcoin at the current price, of course the right time to sell it is in the next bullish season and reportedly 2024 has started,
so it's better to hold for this year and sell in 2024 or 2025, I have also bought some of the altcoins of choice and I hold in the wallet, because the exchange is currently very risky.
but I don't force you to hold it in a wallet other than an exchange, and if you are comfortable in an exchange wallet then save it there and make sure you are ready to take the risk.