This is actually false. The 30-day requirement is placed on consumers. While a consumer must send a validation request within 30 days of the first collection letter that contains the 30-day notice, a debt collector can take as long as he chooses to respond. However, he cannot attempt to collect again until he provides validation. However, if there is a stipulation for tacit acquiescence according to Restatements Second of Contracts ยง 69, the 30 day silence is acceptance rule is valid.
Note that after receiving a timely validation request, a debt collector does not have to validate if he chooses to cease collection efforts. He may never respond at all, or he may send a letter informing the consumer that the file on the account is closed.