BnB is one of the reputable AltCoins that has the potentials for long term holding so if you're interested in investing in the coin then you can always buy and holding whenever it's convenient for you.
Considering the value now and sitting back til the price goes below to your expectations is something that can't be girsnteed because the future prices of crypto currencies is usually unpredictable but all of assumptions. So let your heart lead you Op.