With BOL/SB you can withdraw anytime. They always give you the fair mkt price at the moment you're paid.
For almost every other book, especially 5D, they will freeroll you on price changes. For example if you request a 30k payout right now with the price of BTC being 30k, then if the BTC price goes to 40k, you will get paid 0.75 BTC. But if the BTC price goes to 20k, they'll give you only 1 BTC. The slower the book is in paying, the more you're at risk. 5D for example can take 24hours. And given today's BTC climate, it's imaginable the price could fluctuate as much as the example I just gave.
Anyways, once you have the BTC in your hands, volatility helps and hurts you symmetrically and it's up to you if you want to expose yourself to it.