[skybrian]

If you’re right that Bitcoin will go up forever, there is no need to buy any back because when Bitcoin goes up, it becomes a larger part of your portfolio. To rebalance your portfolio (get back to the same percentage), you need to sell, and there’s never a time to buy unless it goes down again.

But going by the price history, Bitcoin is very volatile, going down as well as up. Keeping it a fixed percentage of your portfolio would result in buying when it’s lower.

(Substitute any volatile investment for Bitcoin.)