#1
Got my guitar around june and sent it for a setup.

After around six months of playing, I feel the string action on my guitar, particularly the 3 higher strings, has raised. There is also slight buzzing on the low E, but nothing that would choke bends or frets, problems which I don't think I had six months ago.

Is it true that the neck changes when you change strings and don't block the trem? I was cleaning my fretboard about a month ago and I didnt put strings on it for around 1 hour, and I never block it if I choose to take all the strings off.

Hopefully my neck isn't permanently twisted or warped because of this.
#2
No. Your neck won't be damaged in any way by anything like that.
Gear:

Guitars: Ibanez SV5470F, Ibanez Xpt700, Fender MIM Standard Stratocaster ('04-'05), Jackson Ps-2
Ashton AG200,
Amps: ENGL E530, Bugera 6262-212,
FX: TC Electronics G-major 2, Behringer EQ700, Morley Volume / Wah
#3
Changes in weather and humidity can cause the wood
and string tension to change!! You can do a simple
truss rod adjustment to fix the problem.
Ibanez AEL10E BLK- W/ Graph Tech Nut, Saddle and Pins
Duncan Woody XL Pickup w/ stock fishman EQ

Schecter C1+ Darksunburst w/ SH-4 (N) & SH-6 (B) 24.75"
Gain boost Switch
11-14-21w-38w-49w-60w D'Addario strings
ENGL Fireball+Savage+Vader Cab