You used "Portfolio Recovery" and "professional manner" in the same sentence. I just wanted the name of your doctor that prescribed your medical marijuana so I can get me some. Portfolio Recovery has a pretty bad reputation on Bud Hibbs and elsewhere.
Opinions vary, here's mine.
I always DV a CA or JDB. Whether the debt is owed or not, whether it's time barred or not. DV is just too powerful of a weapon to discard. A lot of these bottom feeding JDBs are drilling drier and drier wells. They are buying ancient debts at pennies on the dollar, consumers are becoming more and more aware, and I expect CAs and JDBs to step even further outside the law.
A C&D will make they FOAD, but if they stick something on your CRs, time barred or not, then you may be in for a fight. Since you already C&Ded them, DV is effectively off the table.
DV is good right jab and it pays to use it.