Altcoins are really scary, if you can do some research you will see many good altcoins that had very good start and value in 2018 and are still alive today but we never heard anything good from them anymore for some reasons, they are now like ghosts, honestly altcoin investment is more scary, this is why its better to always take profit, most especially from new altcoins, Profit is Profit, either big or small.
You are right but this will change very soon as altcoin season will begin probably early next year 2021, the idea of taking profits is only good when we are in bear market season, but now that it looks like altcoin season is here it's better to hold