if a deadline is not stated in the severance ageement is the deadline of 21 - 45 days held binding

Severance agreements are a matter of pure contract, apart from a few required terms (reading and revocation periods under the Age Discrimination in Employment Act, for example).  That means if the agreement doesn’t have a deadline for you to sign it, you can accept it at any time until the employer withdraws it, which they can do at any time by notifying you of that.  The offer would eventually expire after a “reasonable” period of time, which a judge or jury would probably have to determine under Virginia law.Under the ADEA, the employer must give you at least 21 or 45 days, depending on the circumstances, to consider the agreement.  Even if the severance agreement requires you to sign within 21 days, the employer can always extend the deadline.