Idle temps in 2 months up from 31 to 40

New 7700k build, idle temps were 31 at first with noctua paste, and now around 40 at idle.
Fans are spinning faster because of that, more idle noise.
Why? Did the paske already somewhat dry or something?

Thinking about de-lidding that thing also and replace w metal ultra under ihs....

could be anything.. slightly more dust on the cooler, ambient temp could be higher, something different could be running in the background causing a core to not down clock fully, could be other hardware within the case causing it to run warmer..

even a slight ambient temp change in my room has pretty drastic effects on my cpu idle temps.

I've used the Noctua paste for years now. All over the place. And I've never seen it dry up. So I'd be surprised if that's the cause.

Check your heatsink is still properly attached. Check that your CPU is actually idling, that no background task is keeping it busy. How's the ambient temperature? 2 degrees warmer room will have an impact. Are your fans working properly? Check to see that none of them are faulty.

My experience with de-lidding is that it's great. (On a 6600k with CLU)... I believe the 7700k is similar in that there are no SMC's to cut up. I just eased a razor blade in there - took about 2 mins.

As for why - agree with all above. Could be anything!!

Ambiant is the same, humidity also, processor is at 1-2%, cooler has not moved, fans are fine, no dust, no hardware change.
Oh well, whatever, will de-lid anyway to get to 5+ ghz (and/or lower temps)

Interesting, this just happened to me. Built an open air PC while waiting for a case, idled at 31c with Noctua paste to test everything worked a few weeks ago, and when my case arrived and I retested stuff before putting it in, I was hitting mid 40's at idle in open-air. Ambient in my room was more humid, I so I chocked it up to that. Made a drastic difference beyond the increase in ambient though, I was seeing 15-20c differences in AIDA64 stress testing despite the ambient in my room not increasing by that much.

It's probably ambient in my circumstances, but I'm OCD enough that I think I am going to reseat with some new thermal paste and mod some stuff just because I enjoy torturing myself.

my ambiants and humidity are the same and the temps went from 31 idle to 40 this morning.
could be the intel paste also

I ordered coolab liquid ultra and will do a delid and report temps after delid.
Probably will oc above 5 ghz also after that