Right.The spindown time varies greatly depending on the temperature of the trainer, taking much longer when it's hot.
More heat means the grease in the bearing is less viscous, and the rubber belt is more supple.
You can feel that in resistance mode.
I'm not sure. That depends very much on how trainers handle temperature compensation, I suppose.I wonder if that isn't a factor in why the perfect power (averaging well within the margin of error) starts to drift upwards slightly (3-4% high on average) after about 10 minutes. Probably not enough to notice.
In my experience, it isn't just about time, but about the wattage you put and for how long. E. g. when I have intervals with long pauses, the trainer cools down, which leads to lower rpm for the same watts at the crank.Supposedly 10 minutes of warmup is best (I have seen it written that after a ride is the second best option), but I think it should be more like 20 minutes if you're riding in a cold room.
Most trainers have active temperature compensation, just like other power meters. Elite mentions this explicitly with some models. Exceptions are e. g. Elite trainers with optical torque sensors, because those aren't influenced by temperature as a matter of principle.Wahoo confirmed that Kickrs are most accurate between 15 to 30 C. Curious whether they calibrate it to compensate for drivetrain loss...
AFAIK they do not do anything to compensate for drivetrain loss. (I had asked that question in the TR forum and dcrainmaker replied, and said "No.")