Many people will say it's a bad time right now to invest in Bitcoin because it just hit a new all time high today ($6400) and Ethereum just gain a little bit on value, but for me if you are going to invest and hold it for long term, you should do it as soon as possible and don't wait for the right time, it is always the right time for long term Bitcoin investment because more and more people and business are adopting Bitcoin right now. I'm not a big fan of Ethereum but I also put some money on it for long term.