The clutch system is like brakes: You push on the pedal and something at the other end moves, let go, and it returns. There is a high spot where the air will collect and so that's where the bleeder screw is located. There is a light spring behind the release bearing so it is always resting on the pressure plate fingers (i.e. no take-up gap.) Bleeding seems like an idea, except you said it varies depending on temperature.
Other than bleeding, the only other "adjustment" is this pumping procedure. Based on what I know and described, I am guessing that the pumping jiggles air, the spring, or perhaps helps reposition the static location of the slave/release bearing?
As a last resort, you may have a slave cylinder going bad. In my case, it started to leak, so I knew what was happening. Upon removal and disassembly (destructive, they cannot be repaired) I found that a crimped metal ring to keep the rubber seal in place had loosened it's "grip" and the rubber seal (think of a 2" rubber o-ring but with a square cross section) had started to twist. I am partially making up this theory, but since it twisted first before it started to leak, maybe it is dragging and the resistance to movement is changing it's resting position. I don't really know, but if bleeding doesn't take care of it, there isn't much other hardware that is involved.
