I've got a quandary. I hear mention that centuries of tension and basses do just fine.
I'll agree my basses (and guitars) seem happy for years and years under tension, when I play them regularly and adjust tension to keep them in tune.
But storage seems to be another matter. When my interest in guitar flagged for some years, and I left it in my locker, it ended up with both a bent neck and a bulged belly behind the bridge. The only odd variable I can think of that's in play there is temperature, perhaps increasing string tension when it's cold?
Even a bass neck will bend under string tension (just under 300 lbs - more for my 5-strings) if the fingerboard glue joint fails. I had a bass that all of a sudden had way more scoop than had been carved into it. Turned out, the lower half of the fingerboard had come unglued. I couldn't see a gap but it was enough to allow the neck to bend appreciably. It was caught right away, re-glued and everything straightened out. What would had happened if it had been left over time...?
Most of my making/repairing experience is with bows. When I first camber a bow, pretty much invariably I end up with some twist. Some of it comes from me unintentionally introducing a torque with my hands when bending. But most of it is the wood fibers releasing stress and finding a new normal, post carving, while the lignin is soft in the presence of heat.
A bow isn't as beefy as a bass neck and over time it will eventually lose camber just from normal playing. But again, storage seems to be a special issue. I recently re-cambered my stand partner's spare bow. He's totally in love with his primary bow and never uses the spare if he has a choice. Or takes care of it. So he had left it in his bag both under tension and with the hair mostly gone from the playing side. By the time he asked me to look at it, it had both lost most or its camber and had a hell of a side bend towards the strings. No bunsen burner involved, it just moved over time responding to the hair tension.
And just for kicks and nothing to do with wood, when I bought my Pollman 5-string, my previous Juzek moved (like my partners bow) to backup status. It was bagged and in a closet for years before a hit and run musician or stage crew left the Pollman in the green room on its belly with a broken tailpiece. A mad dash home to retrieve the Juzek got me on stage just in time and it played fine but I found zipper impressions in the varnish of the ribs on one side. That varnish had had 60 years to dry and if I remember right the bag zippers were plastic but time, with the bass laid on its side pressed against those zippers left me with a Frankenbass.
So I don't know if it's over-caution but for basses, guitars and certainly bows, when they're not going to be played for an extended period, I put the tension way down. It's not that I worry about the neck joint failing. I agree, I think your separation was probably a poor glue up in the first place. But I do worry about warping. Or the belly caving. And beware zippers!
BTW, when you get it fixed, please let us know what the verdict was.
