Police can't keep your phone for this long without a warrant. So, there's a legal time limit that the cops can hold on to your phone without a search warrant. And they don't really want you to know that. The courts are going to consider whether or not it was reasonable for a police officer to keep your phone without a warrant for X amount of time. Well, what is X amount of time? It's hard for me to say what the reasonable amount of time is that they can keep the phone without knowing what the situation is. It's not a long time. The cops can't hold your phone for a couple of weeks to waiting for you to consent. They have to get a search warrant within a reasonable amount of time in order to search your phone legally.