The predictions of the coins value will never be accurate not unless you have the power to see whats gonna happen to the future but no one can do that thing so yhose predictions will remain unreliable because we can never know when will be the time will people invest their money in an specific coin. Buy successful coins just like bitcoins of course and ethereum will always be go ups and downs so expect that everytime they reach a new highest value after that the value will now fall and after a few weeks or months they will immediately get up again trust me.
Only the team of big investors can able to give this kind of tips which is going to pump and dump but to finding those teams is not easy. Some people will sell their tips, but still, it's risky to buy tips. So better option is chosen the best coins in the market.