We have no idea how long this will last but for sure it will spike again, and by the way talking about major crash actually its always happened which is after when bitcoin reach the ATH , and also no one can detect and predict when it will happen. And the fact is no one can scape on it,  so must sell if you already gained enough from it and don't ever wait for any sudden drop to ensure that you profits is safe and to avoid ending up in regrets.  'cause market nowadays is very unpredictable,