ROFLMAO. Statute of limitations applies for when they came into his possession.
Statute Of Limitation Is Not An Automatic Bar To Prosecution — It’s An Affirmative Defense
It’s natural to think that once the statute of limitations has run out a prosecutor would not be able to indict someone and then convict a defendant at trial. But that assumption would be wrong.
Despite the expiration of a statute of limitation for a particular crime, the government can still indict you, take you to trial, convict you, and sentence you to prison.
https://www.tpatrialattorneys.com/statute-of-limitations-federal-crimes/
	
 No it is an ONGOING crime for him to keep them in an insecure facility. Sorry. 
  If someone embezzles for years the statute applies to the last date that they embezzled. The statue for Biden won't expire till 2028 which 5 years after the classified documents were returned.