How Long To Hold Onto A Device That Hasn't Been Subjected To A Warrant Yet...

Location: Virginia

My 16yo son is involved in a he said she said situation. I won't get into the details of that other than to say there is no statute of limitations on charges for the accused crime.

He is represented, The detective met with us and we didn't provide much information at all aside from a formal denial of any accusation of wrong doing.

Detectives asked if they could have his phone to make a copy and examine for potential evidence. My son's lawyer responded with "absolutely, after you get a warrant". I did ask the detectives if I can get my son a new phone and they could just have the old one when they are ready to serve a warrant. They said that was fine and I provided them with the phones serial number and imei info so they could tailor a warrant for the specific device if they decide to get one.

This was 3 weeks ago. Radio silence since then. Since I've upgraded my son's phone to a new one, at some point in time I'd like to sell this device and set aside the money towards future legal costs if necessary.

What's a reasonable period of time at which point I no longer have to maintain possession of a device which they have not proceeded to get a search warrant for? My lawyer said put it in my safe and leave it there forever if they don't come asking for it... but am I really required to keep this thing forever? (There's no statute of limitations that would expire for the situation either). Is my lawyer right and I should keep the device basically indefinitely?