This is money and you have all power in your money. After do investment, you can't nothing. You have to trust on your research. So if all in fair-condition, any time you can invest your money in cryptocurrency.
yes, anytime you can do it, but for that you need to do research, if you want big profits, of course you start when prices on the market go down.
what is clear is that you have to be able to take advantage, if you get a better profit, take it, and don't wait too long, because the movements can change quickly.