tennis4 what you are saying is true. The string will continue to relax forever. It just loses most of its tension in the first 4-5 seconds. That is why if you pull again after 5 seconds you can recover that tension loss.
One important point about the lockout is that at lockout the tension does not move any further. The string is just held. It does not matter if it is held by the tensioner or held by a clamp.
I would like to apologize to anyone I have not offended. Please be patient I will get to you shortly.