Wrap time is working time...
It is easy to assume that your representatives use the wrap time to complete any necessary updates on systems, CRM, ERP or pushing communications to the back office. If they find a pre-allocated 'wrap-time' too short to do what they typically need to do then two things will happen;
1 - they will force the customer to stay on the line or on hold whilst the CSR updates the systems, or
2 - they will hurriedly attempt to complete other systems tasks; abbreviating what the customer originally said or needs leaving your records incomplete, inaccurate and suffering as a result
You may be surprised by allowing your CSR's to have an arbitrary Wrap Time, but yes, measuring it. You will quickly learn what the true post call wrap times are; and if you are using accurate and relevant closure or call detail codes then you analytics will tell you a lot. You can identify areas for improvement across your 'business'; something you lose if you have a blanket wrap period for every call. You could be inefficiently long; or too short. Both are bad outcomes for your business.