I think and I have also noticed that if you detune/retune a string sometimes, that affects its characteristics considerably.
So I try to avoid this process. But if for example you do it only once, in order to "play in" a string to have it as a good backup, I guess that this affect would be minor.
Paulino Bernabe Especial 2009
Ramirez 1A 1980
Alhambra Luthier india 2012
Juan Martinez nr 55 (the return @2014)
Yamaha cg 110 (as a kid @88)
student again since 2015, to my degree @..? - God bless!