Really??????? This is news to me. I have used Fender basses since mid-60's (too many to count) and I have NEVER experienced (or know anyone who has) this "s-shaped twist in time" phenomenon. Too much or too little relief, broken / stripped truss rods... sure, but no s-shaped twist to the neck. Currently my oldest Fender is a '79 P with tons of use and the neck is still straight as the day it came home with me. I literally cannot remember the last time it needed adjusting. I live in the mid-west and gig year round in everything from 100+ degree summers through below zero winters.
Oh, I also have a '06 SR505 with low action that hasn't had the neck touched since switching the factory strings to chromes shortly after the initial purchase, it has absolutely no buzz (ever).
You haven't mentioned what environment you store you bass in or how you transport it. I'm thinking something more than just environmental or weather changes may be the cause of your fret buzzing issues. You might want to seek out a different luthier for a second opinion.
If you are the original owner you might want to contact Ibanez about the instability of the neck.
Have you evrr played a 6 string Ibanez? Paper thin neck front to back, like a Rickenbacker.
No I am not the original owner of the Ibanez. I wouldn't pay top dollar for that piece of crap.
I live in a trailer 35 miles north of Palm Springs, not a hermetically sealed vault. The bass is transported 3 times per month to performances in a gig bag in my car.
The notion of "dry heat" out here is a myth. We had one beautiful month in June. Then "monsoon" season set in and has remained for 2 months. (Overcast, humid 80s & 90s, not dry 100s, threats of thundershowers that rarely come.) People out here say it wasn't like that 20-30 years ago.
Last September I had the bass fret leveled & set up for my first gig (in 40 years). Less than a week before the event I got the bass back & it was loaded with fret buzzes.
When I called the local Luthier (not Mo) he said, " I thought you're not an aggressive player!" I am not. He took the bass back, worked on it (blaming the humidity) & when I got it back, more buzzing. He sat on the bass for 2 days making 4 or 5 adjustments, telling me that it keeps changing.
Finally Monday September 27th it came back totally free of buzzing. We had a dress rehearsal (7pm to 9:30pm) everything was fine. Then the clouds rolled in. At 1 am I did some cramming, several fretbuzzes. By bedtime (4:30am) lots of fretbuzzes.
In May I had Mo install a new nut & Kahler bridge. Why? To get the strings away from the neck edges so the c & b strings aren't always pulled & pushed off. This another peeve about the Ibanez. Thanx largely to a fretboard radius of 12" and the strings being so damn close to the edges it was unplayable. Even Mo concurred. Not to mention that a 6 string neck should have a 20" radius, not 12".
I got the bass back with the new nut & bridge on 05/18/14. On Monday (5/20) I played it, & it was loaded with buzzes. I called Mo, he said, " You must be more aggressive with the bass than you said!" Thursday (5/23) all buzzes were gone but one.
I want to stop using TIs, but they are dead enough (along with the SR406's disgracefully dull active preamp) that the fretbuzzes aren't too audible during actual performances.
I started a thread about this. Hardware, setup, etc. Ibanez necks. I will give a shout out again
Again, Marcus Miller bass makes the others look like toys. The nut & bridge are perfect, & position the outer strings so that they stay on the damn neck while playing. I thought the 7.5" radius would be too much, but on this skinny neck it's a perfect fit--so easy to play. The active electronics gimme the MM sound, & tone woods make for a definitive attack. The bass has 2 things it needs: easy release battery compartments, & a balance control & one volume control instead of two volume controls.
Conversely, look at the Ibanez' lack of playable: nut/bridge outer string position, noodley neck, all that need pricey tweeking. Then consider the super dull electronics that have to be replaced or bypassed. Then look at the price!
I have always avoided Fender because they are so hackneyed, I am sick of seeing the Fender headstock, the bodies are large & obtrusive. (I much prefer the sleekness & elegance of the Ibanez.) In HS I bought a Rickenbacker in strict avoidance of Fender. I loved it until performing live with it. Then it got lost & buried in the mix--too light. I had to get a P bass. Now......history repeating itself.