it seems impossible to fall again, because I see that the price of Bitcoin is slowly recovering, so that indicates that soon the price of altcoin will also recover, so I think for now the price of altcoin will not fall again and will instead slowly increase, therefore if you haven't invested in altcoin, so now is the right time for you to invest in altcoin (I recommend top 500 on coinmarketcap).
We believe we are heading a bullrun phase, but a correction or a downfall will always have a chance to happen temporarily. It is impossible that the price of Bitcoin to always rise without any correction. Although Bitcoin price has passed $28k and increased quite significantly, doesn't mean that will be no downfall in the future. I think Bitcoin price is still possible to drop again below $25k temporarily, but it should increase again then. For altcoins prices, it mostly follows the Bitcoin price trend. If Bitcoin price continues to increase, altcoins price will increase gradually. It is clearly seen that many altcoins prices started to increase because Bitcoin price increased currently.
Well, top 500 CMC is too many coins. It is better to focus on top 100 or top 50. I think we don't need to hold too many coins, just hold which coins that seem to have strong fundamentals.