I'm familiar with Hooke's law and Young's modulus at school level, but I need a little more info please, so a quick lesson covering the following situation would be a good start to the New Year.

"Strings" of musical instruments (in my case stainless steel wire of unknown parentage) when first mounted under tension are stretched until they vibrate at the desired pitch.
24 hours later they need tightening a little more as they have "relaxed"(?) a little. Possibly the frame of the instrument has compressed a little as well, but that's another issue. Or is it ?
This process continues, and may be weeks, even months, before the pitch and tone/timbre of the string has settled. Again the changes to the frame will have an input.

Firstly , I suspect that there may be some changes occurring at the crystal level within the metal, so some guidance here would be good.
Secondly, if it were possible to stretch a long length of wire to some appropriate tension, leave it for a period of say a month, then cut the required lengths from that pre-stretched wire, would this process shorten, or even remove the need for the above "ageing" process ?

Happy New Year, everyone,

John

PS via EDIT
This change in the tension of the string is occurring without any degree of playing, immediately after the manufacture of the instrument is completed, and leads to a "settling in" period that I should like to reduce/avoid if possible, before offering it for sale.
All input welcome, particularly on my two points above.