That is not true. They still need probable cause to detain you, and if they have that they can actually hold you up to a max of 72 hrs before they must file actual charges. But for a stop they can only detain you in so long to effect the investagory period. That can take however long but for say a traffic stop should be like 20-30 minutes.

I would LOVE to see a source on this, but I have a feeling I already know where it is coming from.