As we know that the Altcoins market is very dependent on the 3 main coins namely Bitcoin, ETH and BNB, if the 3 coins are green then we can be sure Altcoins are also green, but we must be vigilant if the 3 coins are red so that they immediately move to stable coins is the best choice
Do you mean selling immediately those 3 coins or converting them into stablecoins?
I think it is not necessary, we only need to hold them. If you sell them in a panic, you may regret it once the prices of the 3 coins are increasing high then. Converting them to stablecoins is only needed once you think it is the right time to take profits. Experienced investors don't convert their crypto assets every time they see a drop in prices. It is something not necessary to do, especially if your goal is long-term.