I suspect it's because you change strings so frequently.It takes more than a week for a string to stabilize. Tho' I agree, the sound of new strings is seductive. Generally, I change every 3 months or so, when the strings have been worn enough that the changes are visible at the fretting points and where the fingers /flatpick touch...and the overtones start to sound "off". I play hard, and I play often, in practicing my parts for a celtic instrumental band that meets weekly.

But this is just me, and my guitar. It's getting on to 20 years old (Marc Beneteau Dreadnought)and it has a wonderful mellow tone when the strings get past that bright sound of strings that are new.