The bes time of selling your altcoins is the end of every year . Always in this part of the year altcoin rich ther maximum .
Cryptocurrencies are naturally volatile in price, that is why we can't predict when it will rise and when it goes down. So, for me, sell your coins when the price gets higher than the ICO price and when you think that you really can get a good profit from it. Take that big advantage.
beside that, i think we should know the future of the project. like the current example of pundix, where listing in binance, so i'm sure the price will soar, that's when we sell our assets before it goes down again