Rested strings?

[Matthew Tucker]

This is probably a question without an answer but I'll ask anyway.

I took my 4 year old spiros off my bass to try some weedwhackers for the hell of it. They were on for a week or two. I put the spiros back on tonight - and they sound almost like new - bright, nice overtones, and I like the sound (many don't, I presume). I've done this before, but after a week of playing they go back to sounding dark again, less interesting for me. Its a ply bass.

What's happening here? Is the bass relaxing or the strings? And how can I keep them sounding the way I like them? Maybe i should wind them down every night ...