Both BTC and ETH are great long-term coins. Doing DCA with both of these coins is somewhat my plan for this year along with my crypto trading colleague. They're already proven to come back stronger whenever the market goes down not just once, but many times already. There's no such perfect moment on when to buy or sell BTC or ETH because the crypto market is very unpredictable. No matter what advice you get, they're not perfect. Only you can really decide because it's your money, and just be prepared and fully aware of the risks too.