I think everytime is a good time to buy an altcoins, because you can easily earn profit anytime that altcoin you buy increases its price. But the best time to buy altcoins is when the prices are down, and it clime to increase in the long run.
Never be affected by time, when is the right time to buy altcoin. can be anytime when you are ready to buy and hold altcoin. I agree with you that what is certain is when altcoin is going down the best time you buy it and hold it. You can analyze at CMC or CoinGecko to find coins in the best position to buy,
don't forget to analyze a little to get the most appropriate.My friend, it needs through research. You do not just invest in altcoins because you see the price is down. how are you sure that the point you bought from is the bottom. Well, you can take the risk, but some risks, in my opinion, are not worth taking.
If you are going for the top altcoins, perhaps, the top 10, you can rest assured that with time, you can retrieve back your fund and perhaps et some profits. However, investing in ost of the shit coins around is where you need to do some thorough research and invest what you can afford to lose because you cannot be 100% sure it will be good.