I started an experiment on Wednesday.
I took three matched springs
measured the lengths (1.25")
left one alone
Put a skinny bolt through one with a washer on each side and a nut to compress it to .75"
secured the end of the third and stretched it to 1.75" and used a nail to hole it stretched
It is up in the rafters now for 6 mos.
We will see if after 6 mos I feel like (or a need) to extend the test to a year or more
A more accurate test would be spring tension testing, but our pull tester at work is calibrated and set up for our small medical tools we make, so I can 't use it for playing