If the DOFD on the OC account was more than 7 years plus 180 days ago, any reporting they make to a CRA will never see the light of day in any credit report they issue.
If the SOL has expired, then they have lost the ability to obtain a judgment.
So you could choose not to pay the debt.
However, their could still be reason to pay. Neither expiration of the credit report exclusion period nor the expiration of SOL discharges the debt itself (except for some rare state statutes that actually discharge a debt upon expiration of SOL).
You could choose to rely upon credit report exclusion as sufficient to shield knowledge of the unpaid, delinquent debt from others, but that is a risk you take.
It could possibly still be discovered by other means, such as affiliate sharing of information, or simply asking you when you app for new credit if you have any old, unpaid delinquent debt. Satisfaction of the debt discharges it. The debt collector can also still make future pulls of your CR as long as they still have legitimate collection authority or own the debt.
