What is the current state of the law on the Miranda waiver?

" 'After a valid Miranda waiver, readvisement prior to continued custodial interrogation is unnecessary "so long as a proper warning has been given, and 'the subsequent interrogation is "reasonably contemporaneous" with the prior knowing and intelligent waiver.' [Citations.]" [Citation.] The necessity for readvisement depends upon various circumstances, including the amount of time that has elapsed since the first waiver, changes in the identity of the interrogating officer and the location of the interrogation, any reminder of the prior advisement, the defendant's experience with the criminal justice system, and "[other] indicia that the defendant subjectively underst[ood] and waive[d] his rights." ' [Citation.] [Our Supreme Court has] permitted as 'reasonably contemporaneous' the resumption of an interrogation without readvisement even a day or two after the initial waiver." (People v. Duff (2014) 58 Cal.4th 527, 555.)