If they are 'silent' - not harrassing you ot threatening suit then you wait out SOL unless you can afford to pay in full to prevent a lawsuit CAs have tens of thousands of accounts - and the SOL can pass and they do nothing - no way to make you pay. If SOL is close to expiring then wait it out.
First step is a DV - make them prove the debt is legit, they have a right to collect it, are licensed to collect (if required in your state), etc. If they can not validate they cannot collect on the debt or report it to the CRAs.
Also, you have more leverage on a PFD if the debt is past SOL - it is the only way that they 'can' get any money.