In February of 2009, I received a collection letter from Weltman, Weinberg & Reis Co. on behalf of Hilco Receivables. I promptly sent both of them debt validation letters via USPS CM+RR, giving them 30 days to validate the debt.
Their 30 days were up on March 6th (Hilco) and March 9th (WWR). Since I know CAs can't technically be held to those 30 days, I gave them a little more time on top of the original time so they could validate the debt.
We're a few days short of 60 days now and neither Hilco nor WWR have responded - in other words, the debt was never validated.