BTC is an investment itself, so putting money in is always good... Don't turn to burning massively, but the extent to try some is always worth it if gains continue.
Don't forget that the need to diversify is sufficient, so always reserve your fiat.
It is not always good if you are going to put your money or invest in bitcoin while the price is high. It just depends on the timing upon seeing the price of bitcoin. And if you are lucky enough to buy bitcoins earlier while the price is $800+. But if you do believe that if the price is going to keep on pumping you might need to invest now, remember to invest what you afford to lose only.
I think its still good i he can wait for a long time.. or if he or she long time holder that they can still wait for too long.. buying bitcoins with your alary monthly is one of good idea to make more bitcoins in your wallet so that you can make more profit every time the price is increase// like you said the movement right now in bitcoin is high but its not a problem for long time holders..