It's a common misconception, but string "death" isn't about loss of elasticity due to breakdown of the internal structure of the string.
It's really just a matter of two (competing) factors, tension loss and increasing abrasion. When strings get dented, scuffed up, and notched, the mains don't slide as freely. This results in shorter dwell times, and shorter dwell time creates more impact shock.
This explains why half of all tennis players express dead string as stiff, dead, lifeless, arm breaker etc.. The other half express dead string as that moment when the string has lost so much tension you start spraying to the back fence, because you are playing with a mushy uncontrollable trampoline.
As tension drops, the string bed is getting more comfortable. However, the increasing abrasion creates shorter dwell times which increases impact shock. If you eventually get the mushy trampoline, tension loss has won the battle. Door number two is the stiff arm breaker prize which means that the abrasion factor has won and is dominating the feel of the string bed.
Also worth a mention that all strings lose tension within the first few hours and days after stringing, then again after the first few good whacks. There are some recent co-polys which are exceptions to the rule,but in general, poly loses about 20%, Nylon about 10%, and Gut will lose about 5% before settling in and becoming fairly stable. A 6 pound drop for poly is fairly a moderate loss, which can be arrived at fairly quickly.
More detailed explanation here
http://tt.tennis-warehouse.com/inde...d-but-unhit-poly-go-dead.531883/#post-9282279
How Tennis Strings "Go Dead" — Part 1
The Change in String Properties with Repeated Impacts
http://twu.tennis-warehouse.com/learning_center/deadstrings.php
How Tennis Strings "Go Dead" — Part 2
Do Strings Lose Elasticity with Repeated Impacts?
http://twu.tennis-warehouse.com/learning_center/deadstringsPart2.php