Sell your altcoins based on your selling strategy. The question is what is your selling strategy?

Is doubling your initial capital enough already for you to sell your altcoins? A 50% increase would be enough for you. The term "decent high" is something that you and I will never know because you don't know what the peak of these altcoins are. Some might reach new ATH, and some might not. Set your selling price, and if that reaches, sell and don't even care if the price goes up after selling as long as you made profit off of it. That's regardless of what altcoin you are holding.

As for taking profit and re-invest it into Bitcoin, with the recent drop in the price of Bitcoin (nearing to be below $100,000 again), it's good to buy some Bitcoin IF the money that you're using will be your own, but if you're planning to sell your altcoins to buy some Bitcoin, I don't recommend doing it and would rather hold those altcoins instead, and HOPE like you said. For me, HOPE can't be connected with investing into crypto. Strategies are, and always have a strategy because that would help you along the way.