I wouldn't wait I would just buy and hold. Because why would I wait? We don't know if it's top or not. Even if it is top we will see higher in the future. So just dip in and buy whatever you can.
Hold as long as you don't need to withdraw and buy more as long as you have spare money to invest. There is no other option. Buy buy and buy more until you have decent amount. Then you can wait and enjoy higher prices with as much as Bitcoin you have in your hand.
When you are planning to invest in bitcoin, you shouldn’t just buy all at once and hold, it’s better you have a strategy when investing, and the best strategy is for you to make use of DCA strategy. Am not saying you should wait till bitcoin dumps before you start buying, but even if you will be buying now, then making use of DCA strategy is the best, and if you are planning to invest in bitcoin, then you should be ready to hold for a long period of time.
He is already making use of a strategy which is known as a lump sum investment. I am sure you are familiar with this strategy as well. But if you are not, it is a strategy where an investor decides to front load his portfolio by making a huge buy at once over a certain period of time. That doesn't mean he won't buy more when he comes up with more resources. The strategy is not bad, it is encouraged in a situation where the investor is capable of tampering the money he intend buying bitcoin with and diverting it into something else, or procrastination setting in. So instead of dividing the money and investing through DCA, he goes all in at once just to make sure he has secured the bitcoin the money was intended for. He will make more subsequent purchases, as he comes up with more resources.